Vaginal adenosis is a rare kind of disease without specific symptoms and does not represent a very serious disorder from the beginning. Concerning the etiology teratogenetic dependencies are known which still are interpreted in different ways in the recent literature. The increased number of cases, including those with clear-cell-carcinoma of the vagina, in juveniles after exposition to DES during the early embryonal development shows in particular (Central index for the stilbestrol-adenosis-carcinoma-syndrome in the USA, since 1971) a wrong pathway in the organogenesis of cervix and vagina. This occurs at the interference zone between the epithelium of the Müllerian ducts and the epithelium of the sinus urogenitalis of the female fetus and in so far constitutes the origin of vaginal adenosis. The basics of the possibility of the development of such irregular differentiation and heterotopic dissemination are proven again by the case report of a vaginal adenosis showing the highly differentiated endocervical type. Not every case of vaginal adenosis does signify a precancerous lesion. The separation of the most frequently endocervical manifestation observed from endometrial and intermediate forms might be difficult. A positive distinction is prognostically essential, however, since clear-cell-carcinomas of the vagina are known in occurence with the endometrial type of vaginal adenosis only. Scanning electron microscopy as a method to follow tissue organization reveals the way of differentiation between the various types via ultrastructural analysis for vaginal adenosis is an example for failures of developmental organization. The same analysis is feasible in cytological smears also. The therapeutic requirements of vaginal adenosis depend on the tissular differentiation and the given local extent of the adenomatous lesions.