Woods Hole Group Environmental Laboratories analyzed more than 400 sediment and seawater samples for petroleum hydrocarbons and related parameters in support of a baseline characterization, pre-drill survey, and initial monitoring for an international oil company.  Extract cleanup techniques using alumina chromatography were used to remove potential non-petroleum hydrocarbons from marine sediments; analysis by gas chromatography with flame ionization provided reporting limits on the order of 1 mg/Kg in sediments.  Selected samples were analyzed by gas chromatography/mass spectrometry with selective ion monitoring for a comprehensive suite of decalins, alkylated PAHs, and heterocyclic hydrocarbons indicative of petroleum.  Data will be used for comparing sediment and water column measurements from future monitoring surveys.