Although acute acalculous cholecystitis (AAC) accounts for less than 10% of acute cholecystitis in adult, gangrene and perforation are much more frequent than in the usual case of acute cholecystitis. Since the patients are usually associated with complicated clinical illness, the diagnosis is often difficult and the operation is often delayed. Overall incidence is increasing according to the increasing elderly patients, especially with the cardiovascular disease which is a important predisposing factor of AAC, and the improved survival rates of the critically, ill patients In this paper, we reviewed 17 cases of AAC for recent 5 years in our hospital retrospectively. None of them had recent history of trauma or major surgery. Age was fifty years or older in more than 75% of patients. Male to female ratio was 1.4: l. Right upper quadrant pain with tenderness and fever were the most common symptoms and signs. Leukocytosis was found in 80 per cent of the patients. Associated cardiovascular diseases including hypertension, heart diseases and diabetes were demonstrated in nine of the seventeen patients (53%). Ultrasonography and cholescintigraphy (DISIDA or HIDA scan) were most reliable imaging techniques in the diagnosis. Fifty per cent of the patients with AAC had gangrene or perforation of the gallbladder. Diagnostic delay over 48 hours occured in the 59 per cent of the cases. And the gangrenous change was more frequent in the cases of the diagnostic delay over 48 hours. There was no mortality. In conclusion, high index of suspicion is very important for the diagnosis of AAC, therefore AAC should be considered if an elderly patient with cardiovascular disease complains acute right upper quadrant pain with fever. Once the diagnosis of AAC is made, surgical intervention must be done as early as possible because of the rapid progression of disease.