30 patients were examined: 17 males and 13 females aged between 53 and 83 years (average age 66 years), candidates for large intestine surgery. For 5 days before the operation, they were treated at random, in a balanced way, with cefotaxime (3 g/day intravenously), either alone or associated with rifaximin (1200 mg/day P.O.). Rifaximin, an antibiotic drug endowed with a topical intestinal action, substantially increased the antibacterial activity of the well known and traditional third-generation cephalosporins therapy in the prevention of bacterial infections after major colic surgery. Intestinal bacterial load and pathogenic micro-organisms reduction was substantially increased. Furthermore, a more limited onset of post- surgical complications was observed, together with a better post-surgical clinical course, and a more rapid recovery of normal intestinal functions. The possibility of carrying out an effective chemoprophylaxis by means of an oral drug, such as rifaximin, must be encouraged as, among other things, it substantially reduces the intolerance risk at systemic level, which is nevertheless possible with parenteral antibiotic treatments