An open comparative and multicentric trial was carried out to assess the activity of sulbactam ampicillin combination against no treatment, as a prophylactic agent of post-surgical infection in ob-gyn practice. 100 patients were included in the trial and distributed in two groups. sulbactam/ampicillin 0.5/1.0 g, i.v. was administrated during the surgery and the dose was repeated 6 h. later. No cases of post-surgical infection was detected in the group of sulbactam/ampicillin, while 4 cases were observed in the no treatment group. Sulbactam/ampicillin is an effective and well tolerated antimicrobial agent in the prophylaxis of post-surgical infections.