The effects of alcohol withdrawal on total and segmental transit time were evaluated in 20 chronic alcoholic subjects. After withdrawal, colorectal transit time significantly increased from 24.9 +/- 3.6 to 33.3 +/- 4.5 hours mean +/- SE (P less than 0.01). This was the result of an exclusive increase in rectosigmoid transit time from 2.8 +/- 0.7 to 9.8 +/- 2.1 hours (P less than 0.001). No variations were found in right or left colon transit time. Distal colonic motility is thus a crucial factor in the genesis of diarrhea in chronic alcoholic subjects.