Field and laboratory studies of petroleum hydrocarbons in the tissues of the American oyster, Crassostrea virginica, a primary shellfish resource in the Galveston Bay system, were conducted from 1971–1974. Initial ultraviolet spectrophotometric and gas chromatographic analyses of tissues revealed significant amounts of oil-derived petroleum hydrocarbons from oysters collected at Morgan's Point Reef at the lower end of the Houston Ship Channel. Lower values, when detectable, were found in oyster meats collected at natural and artificial reefs scattered throughout the lower bay system. Laboratory and field studies were conducted to determine uptake and depuration of petroleum hydrocarbons by oysters. Rapid depuration of petroleum hydrocarbons accumulated in field and experimental exposures was found. In oil-free seawater, oysters released saturated chains and most aromatic fractions rapidly with depuration to below detectable levels (0.1 ppm) taking place within 52 days. Transfer of oysters for depuration purposes shows promise of improving the overall quality of this shellfish resource.