Insulin has a trophic effect on pancreatic acinar tissue, so the pancreas might be expected to atrophy in persons who have diabetes. Accordingly, we analyzed the density, contour (smooth or lobulated), and thickness of the pancreas on CT scans of diabetic patients and compared the results with those in control subjects. The prevalence of pancreatic lobulation (incisurae deeper than 2 mm) and its correlation with age in diabetic and control subjects were determined. The thickness of the pancreas was measured at three levels (head, body, tail). Three groups of diabetic patients were examined: 20 insulin-dependent patients, 25 patients not treated with nor dependent on insulin, and 12 patients treated with but not dependent on insulin. A control group included 57 nondiabetic patients. The ages of the control subjects were similar to those of the diabetic patients. The statistical significance of the differences between groups of diabetic patients and control subjects was estimated by using Student's t test for the values of density and thickness and the chi 2-test for the prevalence of pancreatic lobulation. The density of the pancreas in diabetic patients and control subjects was not statistically different. Diabetic patients had increased lobulation of the pancreas. All parts of the pancreas tended to be smaller in diabetic patients, but the degree of reduction varied. It was modest in the patients not treated with insulin, pronounced in insulin-dependent patients, and intermediate in non-insulin-dependent, insulin-treated patients. Moreover, the size of the body was significantly reduced in all three groups, whereas the size of the pancreatic head was preserved in patients not treated with insulin. In conclusion, CT of the pancreas shows that although density in diabetic patients is normal, lobulation is increased. Reduction in size involves the body of the pancreas more than other parts of the gland and is more pronounced in insulin-treated diabetic patients. CT of the pancreas might be useful to predict which diabetic patients will require insulin therapy.