Seventy hospitalized patients with upper urinary tract infections were treated with cefoperazone (2 gm) and sulbactam (1 gm) every 12 hours for three or more days. All but six patients also received vitamin K. Forty of the 70 patients (57%) were cured of infection at one week after treatment, 13 relapsed, 11 had reinfections, and six were lost to follow-up. There were no treatment failures. Escherichia coli was the predominant pathogen (62% of isolates). Overall there was 15% resistance to cefoperazone and all resistant isolates were susceptible to the combination of agents. Synergy was demonstrated in 26% of isolates. One uroseptic patient who had an organism resistant to both study agents, but susceptible to the combination, was cured. Two of six patients who did not receive vitamin K demonstrated abnormal coagulation patterns and one had an associated major bleeding complication. Although 12 of 64 (19%) patients who received vitamin K had at least one coagulation abnormality, there were no significant bleeding complications in this group.