The significance of main pancreatic duct width in the diagnosis of pancreatic disease, was studied in 338 endoscopic retrograde pancreatographies. Two hundred and forty patients referred for suspected biliary disease had normal pancreatograms (Group 1), 60 had pancreatic carcinoma (Group 2) and 38 had a history and pancreatogram compatible with chronic pancreatitis (Group 3). After categorizing patients by decade, in group 1 the effect of aging on the pancreatic duct width in the head, body and tail (F5,234 > 3.71, p < 0.003) was pronounced, especially after the fifth decade. There was a significant difference between groups 1, 2 and 3 in terms of the width of the main pancreatic duct in all three parts of the pancreas (F2,325 > 42.24, p < 0.001). The upper range of normal pancreatic duct width was 8.0 mm, 4.0 mm and 2.4 mm in the head, body and tail, respectively. Abnormal ductograms were wider than the normal ranges in the head, body and tail of the pancreas in 14%, 49% and 59% (p < 0.001) of the patients, respectively. Establishing normal ranges of the pancreatic duct width may help in the diagnosis of pancreatic disease. Measurements in the body and tail, as compared with the head, are a more sensitive indicator of pancreatic duct dilation.