The increase of acute acalculous cholecystitis (AAC) in out-patients produces the review of clinic files of 810 cases of cholecystectomy because of acute cholecystitis; 27 were acalculous (3.3%). AAC was predominant in female sex (20/27) in which the mean age was 37 years. In twelve patients (44%) the cholecystitis was associated with diabetes and hypertension. The clinical manifestations were similar to patients with cholelithiasis and preoperative diagnosis was made in only 33% by ultrasonography. The surgical findings were: Edematous gallbladder without stones, wall thickness and necrosis, as well as perivesicular adherences. In all patients the treatment was immediate cholecystectomy, with morbidity of 14.4% and no mortality. AAC is not only present in critically ill patients, but also is present in patients not hospitalized, and immediate cholecystectomy is the treatment of choice.