Of 739 cholecystectomies carried out from 1971 to 1978, 40 cases revealed intraoperatively a hydrops of the gallbladder. This hydrops was caused in all cases by a stone located in the gallbladder neck or the cystic duct. In 37 cases, the gallbladder contents were examined: clear "white bile" was present in 29 (78%); this was always very viscous. With one exception, all biles were found to be sterile. The pressure in the gallbladder averaged 61.5 cm saline, ranging from 15 to 115 cm. The osmolality of bile was on the average 295 mosmol/kg, thus being roughly isotonic with blood. In three cases, where chemical analysis of the bile was perfomed, bilirubin-, bile salts, cholesterol-, phospholipids, and protein-content were reduced to non-measurable amounts or to concentrations below 1 mg%. It is suggested that the mucosal inflammation following the obstruction to bile flow leads to disturbances in reabsorptive processes, secretion of mucous and a subsequent increase in intraluminal pressure.