Imipenem/cilastatin is a new carbapenem antibiotic with broad spectrum antimicrobial activity. Forty two patients with infections of various types, including skin and soft tissue, respiratory tract, bone and joint, and urinary tract, were treated with this antibiotic in an open noncomparative study. Clinical responses to therapy were excellent and failures were only encountered with infections caused by Pseudomonas aeruginosa strains that developed resistance during therapy. Superinfection rates were minimal as were toxicities. Imipenem/cilastatin appears to be a relatively safe and highly effective broad spectrum antibiotic.