Background and Objectives: The ability to study daily changes in the vaginal flora may provide insight into the pathogenesis of bacterial vaginosis. Because culture of the vaginal fluid is tedious and expensive, the utility of self-obtained vaginal smears for documenting changes in the flora was evaluated. Goals: To validate the adequacy of self-collected vaginal fluid Gram stains and use them to monitor vaginal flora. Study Design: Ten asymptomatic premenopausal women collected daily vaginal smears for 30 days. The smears were Gram stained and interpreted using a standardized scoring system (Nugent criteria). In addition, results from self- and clinicianobtained vaginal smears from 18 women were compared to validate the adequacy of self-obtained smears. Results: Two women had asymptomatic bacterial vaginosis. One woman, who was postpartum, had intermediate flora that toward the end of the collection period changed to Lactobacillus predominant. The remaining seven women exhibited two patterns. One was Lactobacillus morphotypes only; the second consisted of Lactobacillus- predominant days interspersed with days with moderate to high numbers of Gardnerella/Bacteroides morphotypes. There was a significant correlation of the point of change in the flora of this group with menses. Conclusions: The adequacy of self-collected vaginal fluid Gram's stains was validated. Changes in vaginal flora were demonstrated over a 30-day period by use of this methodology.