Erythrocytes and leukocytes were obtained from patients with alcoholic macrocytosis and their lipid composition compared with those from normal subjects. The patients had normal plasma cholesterol and fasting triglyceride levels with mild and fully compensated liver disease. There was no difference in the lipid composition of leukocytes from alcoholics compared with controls. Erythrocytes from patients with alcoholic macrocytosis had increased cholesterol content. The increased cholesterol content correlated with the MCV but there was no correlation between plasma and erythrocyte cholesterol. There was a decrease in erythrocyte phosphatidylethanolamine in alcoholic macrocytosis. There was no change in the fatty acid composition of the phospholipid fraction but there was an increase in the amount of linoleic acid in phosphatidylethanolamine. The double bond index, non-essential-to-essential fatty acid ratio and double bond index to saturated fatty acid ratio for the erythrocyte phospholipids were unchanged in alcoholic macrocytosis. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of erythrocyte membrane proteins from patients with alcoholic macrocytosis and control subjects showed no significant differences.