Three-neutrino oscillations, both in a vacuum and in matter, are applied to the supernova neutrino flux. It is found that oscillations can change the flux substantially, reducing the number of directional events in the Kamioka nucleon-decay experiment and increasing the number of isotropic events in the Irvine-Michigan-Brookhaven experiment. If any of the observed directional events from SN1987A can be attributed to neutronization, then most of the parameter region which solves the solar-neutrino problem is disfavored. The e-\ensuremath{\tau} nonadiabatic solution would be the most probable.