A study to determine the length of the sphincter of Oddi was performed using 148 autopsy specimens with adjacent structures obtained from adults. The median diameter of the common bile duct was 7 mm (range 4-13 mm). The median intramural length of the sphincter measured at gross examination of 75 specimens was 14 mm (range 7-22 mm); the median length of the common channel between the common bile and pancreatic ducts was 3 mm (range 0-9 mm). Longitudinal histological preparations for microscopic examination were made of 73 specimens. The median extramural length of the sphincter was 5 mm (range 1-11 mm). No associations were found between the length of the sphincter, intramural or extramural, and the diameter of the common bile duct, age, sex, presence of stones in the gallbladder or the postcholecystectomy state, nor was there an association between the intramural and extramural length of the sphincter (p greater than 0.05).