Supposing the hernia sac to be peritoneum, intraperitoneal transition of cefotiam (CTM) was examined on 57 cases of infantile inguinal hernia subdivided into 7 groups. 2. After one shot intravenous injection, CTM showed rapid transition into the blood and the peritoneal tissue and even at a dose of 40 mg/kg and 120 minutes later. CTM exhibited an excellent antibacterial activity considering of MIC80 against clinically isolated bacterial strains. 3. Healing by first intention of operative wounds was obtained in all of the cases given CTM without any case suggestive of postoperative infection. No clinical side effect was observed in any one of the cases.