The authors report a case of acute emphysematous cholecystitis (AEC) operated on at the University Hospital of ABC Medical School (São Paulo), with a review of the literature. The infrequency of this finding and the participation of local ischemic factors, associated with secondary infection by gas forming bacteria are pointed out. The authors emphasize the importance of considering this entity potentially more severe than acute non-emphysematous cholecystitis (AnEC) because in AEC gallbladder gangrene is 30 times higher and perforation occurs 5 times more frequently than in AnEC. Besides, the patient with AEC may shows no clinical signs of severity, as in the case reported, where gallbladder gangrene was seen at surgery. In AEC, diagnosis is established usually when the plain abdominal X-ray shows gas within the gallbladder or in its walls. The best results are obtained with cholecystectomy and antibiotic therapy.