OBJECTIVE:To investigate observation of three metronidazol combined with drug for vaginal local application on trichomnas vaginitis. METHODS:195 patients with trichomonas vaginitis were randomly divided into three groups. They were treated with drug for vaginal local application plus single dose or multiple dose of metronidazol(p.o) ,respectively. Then their curative effects were compared. RESULTS:In single large dose of metronidazol group remission rate,cure rate and total effective rate were higher than in multiple low dose group in the first and the second day. Significant difference was noted between the two groups(P0.05) . CONCLUSION:The curative effect of single large dose of metronidazol was better than the multiple low dose. The therapeutic effect of single dose of metronidazol(1.6 g) is similar to single dose(2.0 g) .