Between April and October 1990, photosensitivity reactions were observed in 19 out of 338 patients who were administered lomefloxacin (LFLX) for the treatment of urinary tract infections (UTI) in our hospital. To certify the effectiveness and safety of LFLX to UTI, we carried out a controlled study with fixed dosages and durations. Patients with acute uncomplicated UTI and chronic complicated UTI were enrolled and LFLX dosages of 200 mg b.i.d. for 7 days and 14 days, respectively, were administered. The overall efficacy rates were 100% and 84% respectively. Concerning the bacteriological effect, Escherichia coli and Klebsiella pneumoniae were eliminated in every case, while 3 strains of Enterococcus faecalis 2 strains of Pseudomonas aeruginosa and one strain of Enterobacter cloacae persisted. No photosensitivity reaction or noteworthy severe adverse reactions were observed among 200 cases enrolled in this study of restricted dosages and durations. We, urologists, need to be well-informed about photosensitivity reactions induced by quinolone antimicrobial agents. LFLX was proven to be effective in UTI without showing any photosensitivity reactions when administered by our fixed dosages and durations.