This randomised, double-blind, multicenter study compared the safety and efficacy of lomefloxacin and norfloxacin in adult female outpatients with uncomplicated urinary tract infections. Patients were randomly assigned to one of 3 treatment groups: 400 mg lomefloxacin once daily for 3 days (L3), 400 mg lomefloxacin once daily for 7 days (L7), or 400 mg norfloxacin twice daily for 7 days (N7). A total of 703 patients (age 17-75 years) were enrolled at 21 investigative sites in southern Sweden. Clinical and microbiological evaluations were conducted at the start, 5-9 days and 3-4 weeks post therapy. Patients with quantitative urine cultures of > or = 10(4) CFU/ml of a susceptible pathogen were considered evaluable for efficacy. Escherichia coli and Staphylococcus saprophyticus were the most commonly isolated pathogens. In both L3 and L7 groups, 196 patients and in the N7 group 195 patients met the criteria for efficacy evaluation. At the 5-9 day post-treatment evaluation, 88% of the pathogens were eradicated in the L3 group, 93% in the L7 group and 93% in the N7 group. At the 3-4 week post-treatment evaluation, 81%, 82%, and 85% of urine cultures remained negative in the L3, L7, and N7 groups, respectively. No statistically significant differences between the 3 treatment groups were noted with the exception of eradication of S. saprophyticus, for which the 7 day courses were more effective at 4-9 days post treatment. No persistent pathogen developed resistance to the study drugs. All 3 treatment regimens were equally well tolerated, except for photosensitivity reactions, which were more frequently reported in patients in the lomefloxacin groups.