Urinary tract infections (UTI) due to gram-positive bacteria are fairly uncommon. In order to investigate the efficacy of treatment for UTI secondary to gram-positive rods, we performed a non-comparative study on the effect of cefotaxime in 64 patients with gram-positive UTI. Patients with a history of hypersensitivity to cephalosporins and penicillin as well as patients who had received antibiotic treatment within 48 hours after the administration of cefotaxime, patients with hepatic disease and patients with fatal progressive disease were excluded from the study. UTI was confirmed by positive cultures with a colony count of greater than or equal to 100,000 cfu/ml of gram-positive organisms before treatment with cefotaxime. When sepsis or bacteriuria occurred after two days of hospitalization, the UTI was considered nosocomial. The most common microorganism isolated was Staphylococcus aureus, followed by Streptococcus faecalis. 30% of the patients showed polymicrobic bacteriuria, especially in association with gram-negative bacteria (70%). A high frequency of predisposing factors was present in the urinary tract, mainly obstruction, indwelling catheters, surgery and chronic debilitating diseases. Seven patients developed bacteremia. All patients were treated with cefotaxime i.m. or i.v. at a daily dosage ranging between 4 and 12 g. Urine cultures were repeated five days after the beginning of treatment and again two to three weeks after the end.(ABSTRACT TRUNCATED AT 250 WORDS)