Imipenem/cilastatin as a single agent or in combination with amikacin was used as empirical treatment of severe hospital infections. Twenty-five patients were evaluable for efficacy and the overall response rate was 62% with imipenem/cilastatin alone and 80% with imipenem/cilastatin in combination with amikacin. The highest response rate was obtained in urinary tract infection (75%) and in pneumonia (70%) and the lowest response rate (50%) was observed in bacteremia of unknown origin and in skin and soft tissue infections. Eight failures were observed and seven of them occurred in patients treated with imipenem/cilastatin alone. Two deaths occurred, both in patients with bacteremia. Imipenem/cilastatin treatment was interrupted early in 3 patients because the pathogen developed resistance during therapy and in 2 other patients because of side effects. In our study imipenem/cilastatin proved to be efficacious and well tolerated. The addition of an aminoglycoside to imipenem/cilastatin might improve its efficacy and prevent pathogens from becoming resistant during therapy. Therefore this association would seem to be advisable for the therapy of bacteremic infections and for those caused by difficult pathogens.