Objective The purpose of this study was to compare the efficacy of 2 different doses of tinidazole with metronidazole for the treatment of bacterial vaginosis and to compare the side effects of the drugs. Study Design Women were assigned randomly to receive metronidazole 500 mg twice daily, tinidazole 500 mg twice daily, or tinidazole 1 g twice, all for 7 days. Follow-up visits were conducted at days 14 and 28. Results Five hundred ninety-three women were enrolled. There were no significant differences between the treatment arms. Overall cure rates were 76.8% at 14 days and 64.5% at 1 month. Women who admitted to engaging in sexual intercourse during the study were significantly more likely to have bacterial vaginosis at the follow-up visit. There were no significant differences in adverse events across treatment arms. Conclusion There were no differences in cure rates between metronidazole and either of the tinidazole dosing regimens that were studied. In addition, there were no important differences in the side-effect profiles of metronidazole and tinidazole. © 2011 Mosby, Inc. All rights reserved.