Retrospective study of acute acalculous cholecystitis from 1973 to 1983. Twenty-one cases were found, while in this period 1211 cholecystectomies were performed (incidence 1.7%). Only nine patients developed acute acalculous cholecystitis in conjunction with a life-threatening situation, while in 12 others no acute illness was present predisposing to this type of cholecystitis. In all cases cultured, positive bile cultures were found. As necrosis of the gallbladder wall was present in a high percentage of cases, cholecystectomy is advised when possible. The pathogenesis, prevention and diagnosis of acute acalculous cholecystitis are discussed.