Serum lipids were measured in 30 Finnish and Japanese postmenopausal women. Total cholesterol, HDL cholesterol, LDL cholesterol, apo B and the HDL cholesterol/apo A1 ratio were higher in Finnish than in Japanese women. The LDL cholesterol/apo B and apo A1/apo B ratios were lower in Finns than in Japanese. In serum phospholipids the percentage of arachidonic acid was higher and the percentage of the n - 3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid, and the eicosapentaenoic acid/arachidonic acid ratio were lower in Finnish than in Japanese women. No significant correlations were found between serum oestrone levels and lipid parameters.