SUMMARYAfter a synthetic review of the literature, the Author reports the results of his statistical researches on the parental age of 739 congenitally malformed children born, from 1942 to 1957, at the Istituto Provinciale di Maternità of Milan.Concerning the mongolism it seems proved the influence of some particular factors correlated with the maternal age, while on the contrary the paternal age and the birth-order seem to have no influence. About the other malformations examined in this research the parental age and the birth-order appear without relevance.