The occurrence of transient stomatocytosis observed on peripheral blood smears and by scanning electron microscopy, was studied in 100 alcoholic patients admitted to a general medical ward. 15% of the patients manifested marked stomatocytosis, i.e. 10% or more of the cells being stomatocytes and a further 29% had slight stomatocytosis (3--9%). All patients with marked stomatocytosis had a daily average ethanol ingestion of 100 g or more, and had also more pronounced histological and biochemical evidence of alcoholic liver disease than those lacking stomatocytosis. MCV was significantly higher in these patients, but there were no differences in Hb, serum B12, folate, cholesterol or triglyceride levels. The stomatocytosis subsided gradually during 4--6 weeks of abstinence. Triconcave cells (knizocytes) were observed in 2 patients with terminal alcoholic liver disease. Along with an increased MCV, the presence of stomatocytosis may be a useful erythrocyte indicator of alcoholic liver disease.