The fatty acid composition of 10 species of fish caught off the northwest coast of Australia (latitude 17°S) was examined. All species contained high levels of ω6 fatty acids (9.6-23.1% of total fatty acids) with arachidonic acid being the major ω6 fatty acid (5.9-14.8% of fatty acids). Docosatetraenoic and docosapentaenoic acids of the ω6 series accounted for 3-8% of the total fatty acids. The ratio of ω6 to ω3 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 >30°N). The present data and figures from the literature indicate that the marine food chain in the southern hemisphere contains significant quantities of ω6 fatty acids.