Acute cholecystitis is frequent in the elderly, or in patients with gall stones. Most cases of severe or recurrent cholecystitis need surgery as final therapy. Today, the performed procedure in most cases for cholecystectomy in the western world is laparoscopic cholecystectomy. Only in some cases an open surgery has to be performed. Unclear is, what time point is best, concerning outcome and morbidity of the patient, immediate surgery or initial conservative therapy using antibiotics and symptomatic therapy with cholecystectomy later on. Today the performed procedure is mainly chosen by the fact, what doctor sees the patient first, surgeon or gastroenterologist. This study is performed to evaluate if one therapy is superior.