We report evidence from the Third BATSE Gamma-Ray Burst Catalog that long s) and (T 90 [ 10 short s) gamma-ray bursts (GRBs) represent distinct source populations. Their spatial distribu-(T 90 \ 10 tions are signiÐcantly di †erent, with long bursts having but short bursts SV /V max T \ 0.282^0.014 having di †ering by 0.103^0.024, signiÐcant at the 4.3 p level. This implies SV /V max T \ 0.385^0.019, di †erent spatial origin and physical processes for long and short bursts. Long bursts may be explained by accretion-induced collapse. Short bursts require another mechanism, for which we suggest neutron star collisions. These are capable of producing neutrino bursts as short as a few milliseconds, consistent with the shortest observed timescales in GRBs. We brieÑy investigate the parameters of clusters in which neutron star collisions may occur, and discuss the nuclear evolution of expelled and accelerated matter.