A commonly used diagnostic criterion for sphincter of Oddi dysfunction is delayed drainage of contrast media from the bile ducts at endoscopic retrograde cholangiography (ERC), which is defined as the persistence of contrast greater than 45 min after injection. We performed ERC in 11 asymptomatic post-cholecystectomy volunteers for the purpose of evaluating biliary drainage time. In an attempt to more accurately quantify emptying, concomitant scintigraphy was performed at the time of ERC and contrast drainage. Sufficient contrast mixed with technetium-99m sulfur colloid to completely fill out the intra-hepatic tree was injected (mean volume, 9 ml) and the volunteers remained in the prone position during imaging. The length of time from cholecystectomy, bile duct size, volume of contrast injected, and scintigraphic T1/2s did not correlate with drainage time at ERC. At 45 min after injection the degree of residual contrast filling was scored as: empty in three volunteers, almost empty in one, one-fourth full in 5, and one-half full in two. Therefore, 7 of the 11 asymptomatic volunteers (63%) had delayed drainage. Even if more stringent criteria for delayed drainage were used (ducts one-half filled), 2 of the 11 (18%) had abnormal drainage. The frequent occurrence of delayed drainage in these asymptomatic post-cholecystectomy volunteers challenges the validity of the 45-min delayed drainage criterion for sphincter of Oddi dysfunction.