Naruto Episode 38
Hayate reveals that an unusually large number of Genin got through the second stage of the exam. A series of one-on-one preliminary matches will be held to reduce the number of people. Kabuto drops out immediately upon the notice, blaming his withdrawal on an injury sustained from an earlier part of the test. The preliminary matches begin with Sasuke Uchiha versus Yoroi Akado.
Source: Wikipedia
Naruto Episode 38 – Narrowing the Field: Sudden Death Elimination!
