The viscera and brains of 18 stillborns and dying newborn babies infected with mycoplasmas were examined. The etiological diagnosis was done by direct Coons method using antisera against M. hominis and M. pneumoniae. A high percentage (50%) of congenital malformations in mycoplasma-infected babies was observed. Histological and histochemical examinations of the brains and internal organs revealed marked circulatory disorders and degenerative changes indicative of a pathological process which had occurred. Mycoplasmal infection contracted by the fetus in the uterus or during the delivery may be assumed to be pathogenic. Based on the data from the literature and the own observations it is suggested that urogenital mycoplasmas may exert a teratogenic effect on the human fetus.