Meropenem, a new carbapenem with improved stability in the presence of human dehydropeptidase-I[1], was evaluated in three prospective, multicenter, randomized, controlled clinical trials in North America. We compared the in vitro activity of meropenem and conventional antimicrobial agents for the treatment of intraabdominal, obstetric/gynecologic, and skin or soft tissue infections as well as the responses of pathogens to all of these agents. The trials of the drug for intraabdominal infection were double blind, and those for the obstetric/gynecologic and soft tissue infections were open labeled. Overall, MICs of meropenem for pathogens were lower, and the pathogen response rates were at least comparable to those for the following comparative agents: clindamycin plus tobramycin (for intraabdominal infections); clindamycin plus gentamicin (for obstetric/gynecologic infections); and imipenem and cilastatin (for skin or soft tissue infections). Meropenem has high in vitro potency and covers a broad spectrum of anaerobic and aerobic pathogens.