The content and composition of plasma and erythrocyte lipids from individuals having sickle cell anaemia has been determined. The plasma contains a significantly reduced content of both cholesterol and phospholipid while the ratio of cholesteryl ester to total cholesterol, the distribution of phospholipid classes, triglyceride concentration and the fatty acid content were similar to normal values. However, the free glycerol content of the plasma was eight-fold higher than normal. Erythrocyte lipids contain an elevated level of cholesterol and control levels of phospholipid content, phospholipid distribution and fatty acid content. The plasma was separated by ultracentrifugation into VLDL (density less than 1.006), LDL (1.006 less than d less than 1.063) and HDL (1.063 less than d less than 1.21). Significant decreases in cholesterol and phospholipid were observed in LDL and HDL.