To study the treatment effects of ofloxacin (OFLX) on the patients with complicated urinary tract infections (UTI), OFLX at a daily dose of 600 mg divided into either two or three doses per day, was administered for 14 days to 114 patients with complicated UTI. Among the 114 patients, 67 patients satisfied the criteria for clinical evaluation of complicated UTI. One hundred and one organisms were isolated from these patients' urine. Among them, 82 organisms were eliminated following OFLX administration. Twenty organisms appeared newly by the replacement of organisms. Among them, 6 organisms belonged to Candida sp. As to the overall efficacy of OFLX, an excellent response was seen in 37.3% and sum of efficacy rate was 65.7%. Side effects were observed in 3 of the 114 patients. These results indicate that OFLX is both safe and effective enough to be used for the treatment of the patients associated with complicated UTI.