Unlike the effects of Thalidomide on the developing child, those of DES are not readily apparent at birth. The administration of DES and its sequelae are in this respect a unique medical experience. Fortunately, with the realization that late sequelae occur, the use of the drug in pregnancy has been discontinued and the problems are likely to be self-limiting. The link between DES and particularly the benign changes in the vagina and cervix (adenosis) seems well established. The association between this drug and the development of genital malignancies is less clear, and the very low incidence in the prospective studies in the USA supports this concept. The size of the problem in the UK is small, but clinicians should be aware that it exists. Cases of vaginal adenosis in young women should be investigated and screened appropriately, and preferably referred to centres where colposcopic expertise is available. Treatment of simple vaginal adenosis should be avoided.