ABSTRACT The (U.S.) National Academy of Sciences’ National Research Council (NRC) has completed the third in a series (spanning three decades) of comprehensive examinations of the inputs, fates, and effects of petroleum in the ocean. This most recent study, entitled Oil in the Sea III: Inputs, Fates and Effects (NRC 2002) indicates that changes in petroleum handling practices and production techniques, as well as the introduction of double-hulled tankers, have reduced the size, frequency, and total volume of marine spills over the last decade. As suggested by earlier studies, natural seeps, land-based run off, and atmospheric deposition from marine and terrestrial sources continue to represent the majority of petroleum input to the marine environment. In addition to world-wide estimates, the report includes estimates of the total inputs to both inshore and offshore waters along 17 zones along North American. New estimates indicate that the overall amount of petroleum released to the marine environment may be lower than earlier thought (1.3 million tonnes per year [2002] versus 3.2 million tonnes per year [1985]). The overall lower estimates reflect more accurate and complete supporting information as well as real reductions attributable to advances in marine transportation and oil and gas production techniques. Spillage from vessels from 1990 to 1999 was less than one-third of the spillage during the prior decade, and, despite increased production, reductions in releases during oil and gas exploration and production have been dramatic as well. Chronic releases during consumption of petroleum, which include urban runoff, polluted rivers, and discharges from commercial and recreational marine vessels, contribute 70 percent of the anthropogenic load to the marine environment, worldwide. These releases can pose significant risks to the sensitive coastal environments where they most often occur. Insights have been made from long-term studies of sites of major spills or polluted harbors, but to a large degree the significance (in terms of environmental damage) of the large inputs from land-based sources or other chronic releases is not known. Recent studies, however, suggest that polycyclic aromatic hydrocarbons (PAH), even in low concentrations, can have a deleterious effect on marine biota.