Stomach, intestinal, and colonic transit were measured in males with insulin-requiring diabetes of greater than 10 years' duration to compare with symptoms and to estimate the medical significance. For all diabetics only the symptom constipation correlated with the appropriate regional delayed transit. Diabetics with delayed transit in any region, however, had more overall gastrointestinal symptoms. Diabetics with delayed transit had disease of significantly longer duration than those without delay. Delayed transit was common in the diabetics selected for study with 21 of 54 stomachs, 10 of 20 small intestines, and 14 of 20 colons showing impairment. Of 35 diabetics with impaired transit at one or more locations, only seven were judged of medical importance and five of these responded to treatment. In this study, delayed transit was frequent; in the one fifth requiring management, the symptoms related closely to the region impaired.