Group velocity dispersion was determined for Rayleigh waves between periods of 0.5 and 2.0 sec (Rg) recorded from quarry blasts in southern New England. The paths of these surface waves traverse various geologic structures, and distinct dispersion regions have been identified. Normal dispersion was consistently observed in the period range studied, indicating a superficial layer of relatively low velocity (4.1⟨VP⟨5.5) at least 1 km thick in the upper crust throughout this region. Seismic velocity in this upper layer varies laterally and correlates, to some extent, with geologic features. The observed dispersion also indicates that seismic velocity at depths of 5 to 10 km beneath southern New England varies laterally.