Malabsorption occurs frequently in chronic alcoholics. Alcoholics may malabsorb fat, nitrogen, sodium, water, thiamine, folic acid, vitamin B12 and D-xylose. Malabsorption is due to an abnormal luminal phase of digestion as well as a diffuse functional mucosal abnormality. Malabsorption may, therefore, contribute to clinically significant malnutrition, diarrhoea, folate-deficiency and to abnormalities in tests of xylose and vitamin B12 absorption. Factors producing malabsorption in alcoholics include dietary folic acid and protein deficiency, pancreatic insufficiency, abnormalities of biliary secretions and direct effects of alcohol on the gastrointestinal tract. Many of the absorptive abnormalities are reversed when alcoholics are given a nutritious diet, even with continued intake of alcohol. This highlights the causal role of nutritional deficiencies in the malabsorption of chronic alcoholics.