In a period of 15 yr, 3,650 patients with acute cholecystitis were dealt with. Giving preference to an active conservative strategy in the treatment of patients in the phase of an acute inflammation of bile ducts, the authors applied surgery to 1,500 (41%) of these patients, of whom only 4.8% were emergency or urgent cases. The rest of the patients were operated upon after abatement of the inflammatory process in the biliary tract, following a thorough examination and pretreatment. Postoperative mortality amounted to 6.1% with the total mortality in acute cholecystitis comprising 2.9%. Remote results covering 316 patients treated institutionally in 1965 with a 5 yr follow up period after conservative and surgical treatment are reported. The authors recommend a line of conduct in dealing with acute cholecystitis for wider clinical use, giving reference to a number of advantages it has over an active surgical strategy.