[Cytogenetic background of male infertility].

An account is given of cytogenetic causes of male infertility, on the basis of literature and the authors' own observations. Impairment of sexual differentiation was found to be one of the causes of infertility. The functional mechanisms of the Y-chromosome and H-Y antigen are discussed, in that context. The structural changes in the Y-chromosome were found to provide a possibility of gene labelling and to offer an explanation of the genetic processes underlying various types of infertility. An analysis was made also of male fertility accompanied by aberrations of the other chromosomes. The point is made that in the pathogenesis of male infertility decisive importance should be attributed to chromosomal aberrations, above all to deviations of sexual chromosomes. Thorough cytogenetic examination is absolutely essential unless another causative factor has been clearly established.