Supernovae are the most energetic stellar explosions known. They eject the exploding stars' outer envelopes (in many cases having several times the mass of the sun) into space at speeds of several 1000 km/sec to a few 10,000 km/sec. The ejecta expand into the surrounding interstellar gas, compress it, and in many cases induce star formation. The Principal Investigator proposes to study computationally the interaction between supernova ejecta and the interstellar gas. He also proposes to study certain details of the supernova explosion, such as the matter falling onto the compact object remaining after the explosion. Further-more, he proposes to use the same numerical techniques used in the supernova study to investigate galaxy formation.