Intestinal permeability was investigated with a chromium-51-EDTA (edetic acid) absorption test in 36 non-intoxicated alcoholic patients without liver cirrhosis or overt clinical evidence of malabsorption or malnutrition. Patients abstaining from alcohol for less than 4 days almost invariably had higher intestinal permeability than controls, and in many the abnormality persisted for up to 2 weeks after cessation of drinking. The presence of gastritis did not correlate with the presence of increased permeability. The site of altered intestinal permeability was shown by an in-vitro permeability test to be the small bowel. The increased intestinal permeability to toxic "non-absorbable" compounds of less than 5000 molecular weight may account for some of the extraintestinal tissue damage common in alcoholic patients.