ABSTRACT: Knowledge of the normal vaginal microbial flora is essential in understanding the etiology of female genital tract infections. This study was done to investigate both qualitative and quantitative differences that occur during the menstrual cycle. We studied 34 reproductive age women Iongitudinally. Quantitative cultures were obtained during menses and following the cessation of menses. A greater variety of organisms were found during menstruation. The effect was not selective with respect to aerobes or anaerobes. The total number of bacteria between the two culture periods did not change significantly.