Bacterial vaginosis (BV) is the most common vaginal infection worldwide. It not only causes distressing symptoms but also is associated with costly complications such as preterm birth, STD acquisition and HIV acquisition/transmission. Control of BV has been advocated for decreasing these complications, however this is not feasible due to the fact that currently available treatment regimens are inadequate. BV is characterized by a shift in the vaginal flora from a lactobacillus predominant flora to one in which there are high concentrations of anaerobic and facultative anaerobic organisms. The cause of this shift in flora remains unknown although the epidemiology of BV is highly linked to sexual behavior. Current treatments for BV with metronidazole or clindamycin are suboptimal with cure rates at approximately 70% and high recurrence rates. Tinidazole, which is an antibiotic related to metronidazole, is widely used worldwide for parasitic infections but is not available in the U.S. There is preliminary European data that suggest, perhaps due to its pharmacokinetic profile, that treatment with tinidazole could result in significantly higher cure rates for BV. We propose to study this hypothesis by conducting a clinical trial comparing two different dosing regimens of tinidazole to metronidazole among symptomatic women. In addition, we will measure vaginal and serum concentrations of drug during treatment and correlate with cure rates, short-term recurrence of BV, and severity of infection.