Cefoperazone and ceftazidime monotherapy were compared in a randomized, prospective evaluation of patients with nosocomial pneumonia. These antibiotics were equally effective, with an overall successful treatment rate of 45 of 62 (73 percent) for cefoperazone-treated patients and 50 of 63 (79 percent) for ceftazidime-treated patients (p = 0.41). There was no difference in the incidence of side effects (including hypoprothrombinemia), superinfections, or colonization of the oropharynx with yeast, enterococcus, Staphylococcus aureus, or resistant gram-negative bacilli. When antibiotic administration, and laboratory costs are considered, cefoperazone is less expensive than ceftazidime. Both cefoperazone and ceftazidime are effective therapy for nosocomial pneumonia.