The aliphatic and aromatic hydrocarbon content of seawater and a selection of marine pelagic organisms from the Bransfield Strait, Antarctica were evaluated. The patterns of the hydrocarbons found indicated that their origin was biogenic and there was no evidence for anthropogenic hydrocarbons in the Antarctic marine ecosystem. Hydrocarbons which are constituents of man made materials are present throughout the region but not in the patterns characteristic of anthropogenic origin. Recent reports of an even carbon number predominance in Antarctic marine organisms were not corroborated in this study. A number of biogenic compounds were investigated as suitable markers to monitor pathways of hydrocarbons in the Antarctic food chain. Specific compounds (probably branched chain alkenes) were found to occur at more than one trophic level. Polyaromatic hydrocarbons were present in all organisms but were undetectable in 44% of the seawater samples.