The study compared the efficacy and safety of norfloxacin to those of co-trimoxazole in the treatment of urinary tract infections (UTI). A total of 172 adults, 42 men and 130 women were recruited and randomly allocated to norfloxacin or co-trimoxazole using a double-blind study design. Patients with lower UTI received norfloxacin 200 mg or co-trimoxazole (160 mg of trimethoprim plus 800 mg of sulphamethoxazole) b.i.d. for seven days. In patients with upper UTI, the norfloxacin dose was 400 mg b.i.d. for seven days. Eleven to 14 days after treatment, the bacteriological cure rates were 96.8% and 83.3% and the clinical cure rates were 96.9% and 89.9% for norfloxacin and co-trimoxazole, respectively. A few patients complained of gastrointestinal symptoms but there were few other side-effects and the treatments were well tolerated. In conclusion, both norfloxacin and co-trimoxazole were well tolerated but norfloxacin gave higher cure rates.