OUTLINE: This is a randomized, double blind, multicenter study. Patients receive piperacillin/tazobactam IV over 20-30 minutes every 6 hours. Patients who become afebrile within 48-60 hours after beginning treatment continue to receive piperacillin/tazobactam alone. These afebrile patients continue treatment for a minimum of 7 days, of which 4 must be consecutive without fever. Patients who are still febrile after the initial 48-60 hours are randomized to continue on piperacillin/tazobactam alone or with vancomycin. Vancomycin IV is administered over at least 1 hour twice daily. Treatment continues for a maximum of 28 days in the absence of persistent fever. Patients are followed at 7-10 days after completion of therapy.