In a randomised, double-blind trial two single-dose regimens of ciprofloxacin were evaluated for treatment of acute urinary tract infection (UTI) in women. Fifty-three women received 250 mg and 46 750 mg of ciprofloxacin. Seven days after treatment the eradication rate was 81.1% and 82.6% in the low and high dose groups respectively; the clinical cure rate at 28 days was 64.1% and 73.9% respectively. In women with recurrent UTI a significantly better response was found with the high dose regimen (92% versus 68%; p less than 0.001). It is concluded that a single 250 mg dose of ciprofloxacin is effective for treatment in most women with acute UTI, but in women with recurrent infection a 750 mg dose is preferable.