The light microscopic diagnosis of round-headed spermatozoa is shown to comprise different pathomorphogenetic types that are only distinguishable by electron microscopy. Two types are described, one of them corresponding to the type that was initially characterized by Schirren and Holstein by its globular nucleus and its lack of the acrosomal cap; the other one, with normally shaped nucleus and acrosome in an enlarged headpiece, reveals signs of a primary maturing inhibition.