Summary The vaginal microbiological organisms of premenarchal girls were studied in an effort to determine the etiology of vaginitis and to determine the changes that occur in the prevalence of these organisms when the child is under the influence of an estrogenic substance. Neisseria gonorrhoeae occurred in 21 per cent of the patients and could definitely be incriminated as etiologically related to vaginitis. The chisquare test of significance supported this conclusion. The gonococcus was not recovered in girls who received an estrogenic cream which was applied topically to the vulvar region and in whom an adult-type of vaginal epithelium developed with a concurrent establishment of Doderlein's bacillus and a pH of 4. Trichomonas vaginalis occurred in 5.2 per cent of the patients, but not at all in the control children. This organism is believed to be etiologically related to the vaginitis observed in these cases. The chi-square test, however, did not support this conclusion. It is believed that the sample of data was too small to obtain statistical support of the clinical impression. Estrogenic cream had no effect on the course of infection with this organism. The occurrence of coagulase-positive strains of M. pyogenes var. aureus was similar in both patient and control groups and could not be correlated with the observed vaginitis. No enteropathogenic strains of E. coli were isolated from vaginitis patients. The organism, H. vaginalis , was not recovered from any of the premenarchal patients. A large number of species of various bacteria were isolated from vaginitis patients and from normal control girls in approximately equal percentages. These data when subjected to the chisquare test indicated that the probability of such observations occurring by chance was high and, therefore, any one of these organisms had little significance to the obscrved vaginitis. These data are in keeping with those of other investigators who call such cases “nonspecific” vaginitis. The hypothesis is made that some viral agent or agents e.g., the echo, adenovirus, Coxsackie, or possibly some other as yet unrecognized virus, may be responsible for the clinical entity called “nonspecific” vaginitis.