Water, sediment and microorganisms were sampled at stations along a trackline in the Atlantic Ocean off the North Carolina Coast (USA) at depths of 9 to 5,000 m. Selected chemical and physical parameters were measured. At three of the stations, microorganisms isolated from sediment were examined for ability to degrade a number of petroleum hydrocarbons. Media made up with seawater or salts solution supplemented with nitrate and phosphate were employed in the degradation studies; significant growth and hydrocarbon degradation was observed. Bacteria from sediment samples collected at a depth of 5,000 m showed greater growth and hydrocarbon degradation when cultured in a sea-water medium than in media made up with salts solution. Growth of bacteria in sediment samples collected at two stations was found to be suppressed in sea-water medium when a 1% (v/v) mixture of 19 different petroleum hydrocarbons was added. The hydrocarbon mixture was useful in determining the hydrocarbon degrading potential of microorganisms isolated from the ocean environment.