Pharmacoeconomic assessment of efficacy of different modes of antibiotic prophylaxis was made in 27 patients with diagnosis of acute calculous cholecystitis using method of «cost-efficacy». Patients have taken ampicillin/sulbactam intravenously in the dose of 1,5 g or cephazolin intravenously in the dose 2,0 g. Medicine should be taken in 30 min. before the operation. The most expensive was antibiotic prophylaxis by cephazolin. The coefficient of «cost-efficacy» was 774,2 rubles on 1 unit of efficacy in case of cephazolin and it was 506,1 rubles on 1 unit of efficacy in other group with antibiotic prophylaxis by ampicillin/sulbactam. The authors noted the economical and clinical advantage of antibiotic prophylaxis by ampicillin /sulbactam.