Collisions between disk galaxies embedded in massive halos have been studied by means of numerical experiments. The large three-dimensional n-body programs used for numerical experiments in the dynamics of galaxies and galaxy collisions (Miller 1978; Miller and Smith 1980) have been used in this investigation of the collision and merging of galaxies. The use of the large n-body code is important in a systematic study of the physical processes involved. There are enough particles (105) and the detail in the force field is sufficient to give the necessary resolution. Dynamical and relaxation time scales are well separated. This is particularly important in investigations of the merging process and of the nature of the merger product.