In this talk, I will review the Super-K analysis to distinguish between the νμ→ντ oscillation hypothesis and other exotic oscillation/decay scenarios. All of the tested exotic hypotheses are excluded by the Super-K atmospheric neutrino data at the greater than 4σ level. A limit is placed on the admixture of νsterile states in a ντ, νsterile mixture to be less than 25% at 90% CL. In addition, a 2.2σ tau lepton appearance signal is reported which is consistent with our expectation of νμ→ντ oscillations. © 2003 Elsevier Science B.V. All rights reserved.