The in vitro activity of Men 10700, a new penem, has been compared with that of metronidazole, clindamycin, ciprofloxacin, co-amoxiclav, imipenem and three third generation cephalosporins against 120 strains of anaerobes. The organisms tested comprised Clostridium perfringens, Clostridium difficile, Bacteroides fragilis and speciated members of the genera Fusobacterium, Veillonella and Peptostreptococcus. Men 10700 showed activity similar to that of imipenem, and was more potent than metronidazole against all species except C. difficile and P. anaerobius. The spectrum of activity of Men 10700 suggests this agent may be useful for treating infections caused by anaerobes. (C) 1998 Elsevier Science B.V. and International Society of Chemotherapy. All rights reserved.