Twenty patients, 14 males and 6 females, developed acute cholecystitis while recovering from other operative procedures. A wide variety of procedures preceded the cholecystitis, and more than half the patients had prolonged, complicated postoperative courses. Most patients had right upper quadrant pain and tenderness and decreased bowel sounds. Right upper quadrant mass, distention, and jaundice were also common. The white blood cell count, serum bilirubin, glutamic oxalic transaminase and alkaline phosphatase were elevated in the majority of the patients in whom these were measured. Cholecystectomy was done in all cases and the common bile duct explored in 4. All specimens showed acute inflammatory changes, and 7 were partially gangrenous. Only one-half of the patients had cholelithiasis. Bacteria were cultured from 9 of 16 specimens, and a preceding infection, in which the same organism was cultured from bile, was present in only 4 patients. Many patients were elderly and had had long, complicated courses after their initial operation which may have led to decreased perfusion and tissue hypoxia, making the gallbladder susceptible to any insult.