The fatty acid composition of 10 species of fish caught off the northwest coast of Australia (latitude 17 degrees S) was examined. All species contained high levels of omega 6 fatty acids (9.6-23.1% of total fatty acids) with arachidonic acid being the major omega 6 fatty acid (5.9-14.8% of fatty acids). Docosatetraenoic and docosapentaenoic acids of the omega 6 series accounted for 3-8% of the total fatty acids. The ratio of omega 6 to omega 3 fatty acids in these fish varied from 0.38 to 0.93, compared with an average ratio of 0.16 for fish from the northern hemisphere (latitude greater than 30 degrees N). The present data and figures from the literature indicate that the marine food chain in the southern hemisphere contains significant quantities of omega 6 fatty acids.