Sasuke's first major mission was escorting the bridge builder, Tazuna, to his home in the poverty-stricken Land of Waves. Soon after setting out, Sasuke showed exceptional skill when attacked by the Demon Brothers, even taunting Naruto for being shocked and useless during this encounter. When they later had a tree-climbing exercise to improve chakra control, he managed to stay ahead of Naruto for a good length of time, but as Naruto began to catch up, they started to push each other's limits. His skills improved, Sasuke was almost able to compete with Haku, who was extremely dangerous because of his extreme speed and dexterity. It was during this battle that Sasuke reawakened the legacy of his clan, the Sharingan, and even selflessly put himself in the way of Haku's attack on Naruto to protect him. Although he claimed his body had moved on its own, his actions showed that he was willing to put himself in mortal danger for Naruto's sake. Although it appeared that Sasuke had died in the process, it was later revealed that he was merely put in a temporary death state.
Before the Chūnin Exams started, Sasuke fought Rock Lee, who easily overcame the power of his Sharingan through an amazing display of speed and taijutsu prowess; for if the user can't physically keep up with the target then the Sharingan is useless. However, before the finishing blow could be given, Might Guy interrupted the match and punished his beloved student for using a forbidden technique in a normal fight. In the first part of the exam, Sasuke realised that, to succeed in the written test, it is required to cheat without getting caught, as the written exam tests a ninja's information-gathering ability. Sasuke was shown using the Sharingan to copy the movement of a student in front of him, effectively copying the answers. In the second test of the Chūnin Exam in the Forest of Death, Sasuke was attacked by Orochimaru. Recognising that they were no match for Orochimaru, Sasuke tried to surrender. However, Naruto stopped him, attacking Orochimaru regardless of the clear difference in strength, and taunting Sasuke just as he had earlier taunted Naruto. This spurred Sasuke into action, giving him the resolve to defeat Orochimaru. Impressed, Orochimaru put his cursed seal on Sasuke's neck during the battle as a reward, causing Sasuke so much pain that he fell unconscious. As the seal attuned to his body, he had nightmares, and, when he woke up, was immersed in its power. He immediately saved Sakura from the attacking Otogakure genin, effortlessly defeating them and going so far as to break Zaku's arms. Recognising that the cursed seal had apparently corrupted him, Sakura hugged him and pleaded for him to stop. He relented, and the seal receded. Sasuke was surprised by his own sudden burst of strength.
In Part II, Sasuke is revealed to have saved Karin from a bear during the second phase, but he left her alone since he didn't need her scroll.
Sasuke's match up in the preliminaries was against Yoroi Akadō. Before the fight started, Kakashi warned Sasuke that, if his cursed seal got out of control, which would happen if he used any chakra, he would need to be removed from the competition. The match started with Yoroi absorbing what little chakra Sasuke had left through his hands, and with Sasuke being in constant pain from his Cursed Seal. Having only one option, and remembering his previous encounter with Rock Lee, Sasuke used the Lion Combo. Yoroi was knocked out, and Sasuke advanced to the next round.
Following his win, Kakashi took Sasuke away to seal the Cursed Seal, but made it a point to tell him that the seal would only remain active as long as Sasuke wanted it to. Not convinced that his words would deter Sasuke from seeing the Cursed Seal, and Orochimaru, as a source of power, Kakashi used the month leading up to the final rounds to teach him the Chidori. At the same time, knowing Sasuke would be facing Gaara, he helped Sasuke to emulate some of Lee's speed. After showing up late for his match with Gaara, Sasuke demonstrated the fruits of his training, even managing to break through Gaara's defences and injure him. Before the match could finish, however, it was interrupted by the start of Orochimaru's attack on Konoha.
With the start of the invasion, Gaara fled the village with his siblings, and Sasuke was sent after them by Genma. Sasuke chased them and, after short battles with Kankurō and Temari, Sasuke caught up with and fought Gaara. Sasuke used Chidori, once again managing to wound Gaara, who by now had started to transform into his half Shukaku form. The form, however, allowed Gaara to quickly recuperate from the attack, putting Sasuke on the defensive since he no longer had the chakra reserves to use Chidori again. With Gaara's resolve to kill him growing increasingly stronger, Sasuke had no choice but to tap into the cursed seal in order to use another Chidori. However, this had no effect against Gaara, and Sasuke was left exhausted. Unable to move, Sasuke was saved by the prompt arrival of Sakura and Naruto. Sasuke watched Naruto's fight with Gaara unfold, becoming jealous of Naruto once he claimed victory. Later he attended the Third Hokage's funeral
After the failed invasion, Sasuke went to see Kakashi, and later was seen reading the stone tablet in the Naka Shrine. When he arrived at Kakashi's house to see him again, he found his teacher in a coma. Although nobody in the room was willing to tell Sasuke of what had happened, Aoba Yamashiro soon arrived and let slip that Itachi had returned to the village in search of Naruto. Determined to find Itachi and to save Naruto (by order of priority), Sasuke hurriedly rushed outside, tracked his team-mate down, and found that Itachi was already there. Despite his best efforts, including the use of Chidori, none of his attacks were able to hit Itachi. Itachi tormented Sasuke physically and mentally, belittling him for still being too weak, eventually leaving Sasuke with a broken wrist and mind. Sasuke then fell into the same coma-like state as Kakashi, trapped in Itachi's "Nightmare Realm". Guy appeared to take Sasuke back to Konoha, however, it was not until Tsunade returned to Konoha that he recovered.
In the anime, after Sasuke's recovery from Itachi's Tsukuyomi, Team 7 was assigned a mission in the Land of Tea without Kakashi. During the mission, they encountered Idate Morino, the client they must protect during his race in the Land of Tea. Near the end of the race, they also encountered Aoi Rokushō, who attacked them. Sasuke's Chidori was ineffective with Aoi's lightning sword; though it made a crack. When seeing Naruto use the Rasengan, not only was it the first time he saw it, but the Rasengan proved strong enough to destroy Aoi's sword and defeat him. At the end, Idate won the race and Team 7 left the Land of Tea, Sasuke resulting back in the hospital for his injuries during the fight with Aoi. Unlike other filler arcs, this arc actually affected the story, as it gave more reason for Sasuke to be irritated that Naruto was becoming stronger. Aoi's words about Sasuke being the weakest member of the Uchiha clan also acted as a catalyst to Sasuke's desire for power.
Angry that Itachi was still so much stronger than he was, and envious of the fact that Naruto had gotten stronger in such a short period of time, Sasuke challenged Naruto to a fight. Although they were stopped by Kakashi, their brief exchange was enough to show Sasuke that Naruto's Rasengan was more damaging than his Chidori. Kakashi lectured him about using Chidori on his own friends, but, before this could fully sink in, Sasuke was confronted by Orochimaru's Sound Four, each of whom had their own cursed seal. Amazed by their abilities, which they claimed to have received from Orochimaru, Sasuke was left with their offer of escorting him to Orochimaru so that he could get stronger.
To gain the power he so desperately wanted, Sasuke decided to take Orochimaru up on his offer, turning his back on Konoha in the process. As he snuck out of the village, Sakura found him, and soon understood the magnitude of what he was about to do. Desperate not to lose Sasuke, Sakura did anything and everything she could think of, confessing her love for him and even offering to help exact revenge on Itachi. Sasuke's cryptic last words before swiftly knocking her out and departing were, "Sakura… thank you." Sasuke left with the Sound Four, who soon afterwards advanced his Cursed Seal to its second level, a process that left him unconscious for most of their Soon after Sasuke woke up, he was found by Naruto. Sasuke was glad to see Naruto; after slaughtering the Uchiha clan, Itachi had told Sasuke that he would only be able to match him in battle after he had obtained the Mangekyō Sharingan, which could only be attained by killing one's best friend, which was now Naruto for Sasuke. Naruto refused to accept that Sasuke would do this or his other reasons for pursuing Orochimaru, choosing instead to drag Sasuke back to the village by force if he had to. They subsequently engaged in battle, with Sasuke initially having the upper hand thanks to his cursed seal and Sharingan. When he managed to pierce Naruto's right shoulder with his Chidori, however, the Nine-Tailed Demon Fox's chakra kicked in to protect Naruto, giving him a massive power increase.
With the Nine-Tails' chakra now active, Naruto easily tossed Sasuke about in an attempt to knock some sense into him. Sasuke merely retorted that Naruto could never understand what it was like to lose family members, as he had never had them to begin with. Naruto reasoned that Sasuke was like a brother to him, therefore he would not let him destroy that bond. Sasuke's Sharingan evolved to its final level at that point, tipping the battle in Sasuke's favour because he was able to predict Naruto's movements. The Nine-Tails' chakra once again came to Naruto's rescue, enveloping him in a fox-shaped shield of chakra and boosting his power once more. With the Nine-Tails' chakra shield, Naruto was again more than Sasuke could handle, even with his Cursed Seal active. To counter Naruto's power, Sasuke activated the second stage of his cursed seal, becoming a demonic figure with a pair of huge, hand-like wings sprouting from his back. Naruto attacked with his Rasengan (enhanced by the Nine-Tails' chakra) and Sasuke with his Chidori (empowered by the Cursed Seal). Upon impact, a massive dome of black energy formed around them. Sasuke punched Naruto in the chest at the last second (instead of impaling him with what was left of his Chidori) and knocked him out, while Naruto opted to scratch Sasuke's forehead protector, something Sasuke had said he wouldn't be able to do at the start of the fight.
After the energy dome dissipated, Sasuke was shown to be the victor, now standing over an unconscious Naruto. He considered killing Naruto, but couldn't find himself to do it. He also realised that doing so would be exactly what Itachi wanted him to do. Leaving behind his scratched forehead protector, which had fallen off after Naruto's last attack, Sasuke made his way to Orochimaru. While doing so, Sasuke resolved to surpass Itachi in his own way, instead of relying on the same skill Itachi used.
Sasuke débuts in Part II during a meeting with his replacement in Team 7, Sai. When Sasuke shows a lack in interest for knowing who Sai is, the latter inadvertently provokes him by stating that he might be able to get along better with Sasuke than he did with Naruto, and Sasuke traps Sai in a genjutsu exuding a large amount of killing intent. Sai is amazed that even an emotionless person such as himself was affected by Sasuke's gaze, channeling through his Sharingan. When Sai comments on how Naruto and Sakura have been searching for him, Sasuke once again regards him with indifference in attitude.
Later, when Team 7 infiltrates one of Orochimaru's hideouts successfully under the leadership of Yamato, Sai, acting on his own, locates and enters Sasuke's room while he was resting in a bid to assassinate him as ordered by his superior in Konoha's Root faction, Danzō Shimura. However, after spending quality time in Team 7, especially with Naruto, Sai comes to understand the meaning of bonds of friendship, and disregarding his original secret mission of killing Sasuke, he states to the latter that he wants to repair his and Naruto's bond. Enraged on being disturbed, Sasuke destroys the room, drawing Naruto, Sakura and Yamato to their location. Despite this being the first time in nearly three years that they had seen each other, Sasuke expresses his usual indifference towards his former team. Unperturbed in the prospect going home to Konoha with them, Sasuke engages them in battle, showing off his increase in speed and improved abilities.
Sasuke's encounter with the Nine-Tails.
The new Team 7 are little match for him, mostly due to the team's exhaustion with Naruto's four-tailed form (that he had previously used to battle Orochimaru), causing Naruto to begin struggling with the Nine-Tails' chakra in his mind. To the surprise of both Naruto and the Nine-Tails, Sasuke uses the heightened prowess of his Sharingan to enter Naruto's subconscious to meet the Nine-Tails itself, finally discovering the true source of Naruto's strength. The Nine-Tails appears to be impressed with Sasuke's growth and ability, but as it criticises his chakra being as "sinister" as that of another Uchiha it had encountered before, Madara Uchiha, Sasuke coldly dismisses any relation to that person and uses his Sharingan to suppress the Nine-Tails back into it's sealed cage. The Nine-Tails concludes that this was probably its last meeting with Sasuke, so it warns him not to kill Naruto, for he would only end up regretting it. Back outside, Sasuke decides to finish off his former team-mates, starting with Naruto, only to be stopped by Orochimaru. Paying heed to Orochimaru's plan to use Team 7 and other Konoha shinobi to thin Akatsuki's numbers, Sasuke leaves with him and Kabuto.
Sometime later, Orochimaru tests Sasuke's abilities by having him battle hundreds of Otogakure ninja with no compassion or mercy, a task he completes without taking a scratch and without killing any of them. When inquired about the latter part of the scenario, Sasuke remarks that the only person he wants to kill is his brother, Itachi, and leaves to his training room. Soon afterwards, as Orochimaru reaches the limit of his present "vessel" containing his soul, which starts degrading his health, he is notified by Kabuto that the time for his ritual to take over Sasuke's body is near. As Kabuto leaves to get some medicine, a vulnerable Orochimaru is unexpectedly attacked by Sasuke, who announces that there is nothing else that he could learn from Orochimaru, and that he is unworthy of having his body or the Sharingan. Although Sasuke appears victorious after a brief scuffle with Orochimaru's true snake-form, he is nevertheless brought to Orochimaru's subconscious for his body-stealing technique. Having severely underestimated Sasuke, it is Orochimaru, in turn, who is absorbed to a dormant state within Sasuke, who is able to reverse the process using his Sharingan and hence, gains access to all of Orochimaru's abilities.
With Orochimaru gone, Sasuke goes ahead with his plan to locate and kill Itachi, by first recruiting some of Orochimaru's former test subjects - Suigetsu Hōzuki, Karin, and Jūgo - on the pretext of granting them virtues for their themselves after the success of their mission (Suigetsu wants to obtain Samehada by killing Itachi's Akatsuki partner, Kisame Hoshigaki; Karin wants to be with Sasuke due to her massive crush on him; and, Jūgo wants to see if Sasuke was indeed worth of his dear friend, Kimimaro's sacrifice), and dubs their team Hebi. And immediately afterwards, Sasuke had his team split up and learn of Itachi's potential whereabouts. While searching alone, Sasuke is found by Akatsuki members, Deidara and Tobi, with the former wanting to kill him for defeating Orochimaru himself. Using his Sharingan and lightning-based techniques, Sasuke manages to counter most of Deidara's attacks, fueling his pre-existing hatred for the Sharingan, stemming from his past encounter with Itachi, even further, which to him could not see or admire his "art". As a last ditch effort, Deidara uses C0 to try blowing himself up along with Sasuke in a titanic explosion, which obliterates everything in the nearby vicinity. Sasuke, however, summons Manda in time and uses his Sharingan to have the great serpent shield him from the explosion, at the cost of his life. After recovering from his wounds, Hebi continues onto one of Akatsuki's lairs, where Sasuke finds a crow clone of Itachi which expresses admiration over Sasuke's growth in power and tells him they will have their battle at the Uchiha Hideout, leaving the rest of Hebi behind to deal with Kisame.