During Ocean Drilling Program Leg 204, nine sites were logged on the Oregon continental margin, where one of the objectives of the integrated downhole logging program was to determine the distribution and saturation of gas hydrates and free gas in an accretionary ridge and adjacent slope basin. Downhole logs measured at Sites 1244, 1245, and 1247, drilled on Hydrate Ridge, were analyzed to constrain the physical properties of in situ gas-hydrate-bearing sediments. Saturations of gas hydrate in pore space are estimated from shear-wave (S-wave) velocities using the modified Biot-Gassmann theory, referred to as the BGTL. The average gas hydrate saturations are 10%, 10%, and 6% for Site 1244 (76-127 meters below seafloor [mbsf]), Site 1245 (73-129 mbsf), and Site 1247 (74-129 mbsf), respectively, and are comparable to estimates from downhole electrical resistivity logs. Free gas saturations were also estimated from the Biot-Gassmann theory with parameters derived from the BGTL using compressional-wave (P-wave) velocities and from elastic moduli using both P- and S-wave velocities. The exact amount of free gas is difficult to determine because of the uncertainties associated with the mode of gas distribution (patchy or uniform), but both methods provide comparable estimates for free gas saturations. This study suggests that free gas coexists with gas hydrate in the gas hydrate stability zone at these sites. This is the first reported evidence for coexistence of gas hydrate and free gas away from the summit vents.