A pilot study was conducted of males 40-45 years old from rural areas of three countries to study the long-term effects of dietary fats on the lipids of plasma, red blood cells (RBCs), and platelets. Differences were observed in cholesterol and phospholipid levels of plasma. Total phospholipids of RBCs and platelets were similar in all three countries. The pattern of individual phospholipids of RBCs in the Finnish and Italian samples differed from the American samples. In all plasma and RBC glycerolphospholipids, the monounsaturated fatty acids were highest in the Italian and the saturated fatty acids were highest in the Finnish samples; PUFAs were highest in the USA samples. Platelet glycerolphospholipids followed similar fatty acid patterns. We concluded that the fatty acid compositions of the glycerolphospholipids of plasma, RBCs, and platelets reflect the major dietary fatty acids.