A sampling and analytical program, supported by the Office of Radiation Programs of the U.S. Environmental Protection Agency, was initiated in August 1977 to determine the radionuclide concentrations in water, biota and sediment near a deep water (914–1829 m) radioactive disposal site located southwest of the Farallon Islands, west of San Francisco Bay. Specifically 137Cs 239,240Pu, 90Sr and 238Pu were determined in two water samples, 137Cs, 239,240Pu and 238Pu in tissues from ten invertebrates and fourteen fish collected near the disposal site, and in tissues from five invertebrates and three fish collected at a shallow (92 m) station, and 137Cs, 239,240Pu and 238Pu in six box cores and seven cores collected by a submersible. The sedimentation rates were determined by the 210Pb-210Po methods on cores from three sites. Strontium-90 was determined in selected biological and sediment samples. The results showed that 137Cs, 239,240Pu and 238Pu were found at low concentrations (max 0.142 pCi/g 239Pu) in the skin, viscera, and G.LT. contents for some of the fish collected. The edible muscle for the fish generally contained levels at or below the sensitivity limits of 0.005 pCi/g dry 239,240Pu. The sediments contained maximum concentration levels of 0.14 pCi/g (dry) 137Cs in the surface section of the box cores. The 239,240Pu concentrations were measured as deep as 16 cm in certain sediment cores indicating rapid vertical transport, possibly by burrowing organisms. The 210Pb concentration profile also showed high effective sedimentation rates of 1–3 mm/yr and possible mixing of the upper sediments. The submersible cores taken near the canisters indicated loss of the surface layers during collection but contain 2–20 times greater integrated deposition than the expected fallout levels of 1.8 ± 0.6 mCi/km2.