During Leg 204, three near-offset vertical seismic profiles were acquired at sites representing different parts of the gas hydrate system at South Hydrate Ridge. The results generally confirm precruise estimates of velocity, resulting in only minor changes in estimates of depth to key reflections. Although velocities are generally quite low throughout the region, the only significant velocity inversion in the VSP data is associated with a relatively coarse grained and volcanic-ash-rich stratigraphic horizon (known as Horizon A) that appears, on the basis of a variety of different data sets, to be the major conduit feeding free gas to summit vents. This horizon appears as a strong reflection that can be traced regionally in the 3-D seismic reflection data. Bulk density and shear wave velocities from logging data indicate the presence of a second gas-rich zone also associated with volcanic ash at Horizon B´, another strong reflection that can be mapped in the 3-D seismic data. The strong effect on VS measured in sonic logs in Horizon A and Horizon B´ indicates a decrease in shear modulus of nearly a factor of 10, indicating that these zones are overpressured. No regional thick free gas zone is present, in contrast to results from two previous VSP studies in gas-hydrate–bearing regions.