Treatment options for bacterial vaginosis are numerous, however for urinary tract infection (UTI) by Gardnerella vaginalis have been not reported. Our purpose was to compare the efficacy and treatment complications of oral metronidazole versus oral ampicillin for treatment of this condition in a prospective randomized, nonblinded study. Fifty-seven women who had symptoms of UTI and a positive culture for G. vaginalis were enrolled in the study. Only forty-five subjects were considered valuable: 25 treated with oral metronidazole 500 mg twice daily for 7 days, and 20 with oral ampicillin 2 g for 10 days. Positive culture was defined as the presence of 10(4) or 10(5) UFC/ml of G. vaginalis in pure culture in HBT media. The clinical and bacteriological cure rates were 92% and 96% respectively for metronidazole and 90% in both for ampicillin. Chi-squared analysis reveals no statistical significance between two treatments. Adverse events were common in-patients treated with metronidazole whereas relatively few side effects were experienced in-patients treated with ampicillin. Ampicillin is effective, safe and well-tolerated therapy for UTI by G. vaginalis. In contrast oral metronidazole is effective but no safe and bad-tolerated therapy for the same condition.