In a large multicentre study of 429 patients with the usual signs and symptoms of non-specific vaginitis (NSV), we studied the effect of different doses of metronidazole. The patients were divided into five treatment groups as follows: group A was given 400 mg metronidazole three times daily for seven days, group B 2000 mg as a single dose, group C 2000 mg on days 1 and 2, group D 2000 mg on days 1 and 3, and group E was given 1200 mg metronidazole once daily for five days. At follow up examination four weeks from the start of treatment, patients in groups D and E showed the best clinical results with cure rates of 94.0% and 93.6% respectively. In addition the rate of reisolation of Gardnerella vaginalis was lowest in group D. We therefore recommend metronidazole 2000 mg on days 1 and 3 as routine treatment for non-specific or vaginitis associated with gardnerella.