Autoproteolysis of human spermatozoa produces oligopeptides with oligosaccharide chains of the N-glycosidic-linked type that are released from the "surface exposed" parts of glycoproteins. The products eluted in the previous washing of the spermatozoa have the same composition and solubility characteristics as the oligopeptides from the digestion. This suggests that autoproteolysis is a constant process that normally occurs on the spermatozoa membrane. The cytochemical characterization and localization of the N-glycosidic-linked oligosaccharide receptors on the human spermatozoa membrane after digestion, in the presence or absence of seminal plasma, indicates that only part of the oligosaccharides are cleaved. Their distribution on the different zones of the spermatozoon changed as the probability of detecting these receptors in the intermediate segment increased after proteolysis; this indicates that in this zone the receptors are cryptic ones that become exposed by the action of the proteolytic enzymes. In the presence of seminal plasma most receptors on the acrosome are eliminated.