In this study, we analyzed background factors and clinical courses of 31 patients having 32 episodes of urosepsis, which was defined as the disease when the same species of bacteria were simultaneously isolated both from urine and blood in a febrile (> or = 38 degrees C) patient. Most of the patients had a malignant disease. These patients were classified into 3 groups by febrile patterns, based on [responder], [partial responder] and [non-responder], [non-responder] was one in which fever persisted for more than 7 days. Background factors such as those of bacteria and host were compared among the three groups. Pseudomonas aeruginosa was more frequently isolated from both urine and blood of patients having not only the [responder] but also the [non-responder]. Patients having the [responder] and [partial responder] had a higher frequency of isolation of Escherichia coli (E. coli) from urine and blood, suggesting that urosepsis caused by E. coli may respond more easily to antimicrobial chemotherapy. While the direct cause of urosepsis was not identified in 6 patients, manipulations of the urinary tract were a direct cause of the disease in all 26 other patients. An indwelling catheter in the central vein or urinary tract alone did not influence the clinical courses of patients. However, when patients with respiratory or renal dysfunction, or a cerebrovascular accident had an indwelling catheter, the urosepsis was intractable for antibacterial chemotherapy. Antimicrobial chemotherapy using a single agent was effective in all patients having the [responder]. Combination chemotherapy or alternation of agents was eventually needed for treatment in more than half of the patients with the [partial responder] or [non-responder]. No patients died from the disease.