Immunoblotting of a repertoire of sperm antigens reacting with antisperm antibodies present in sera of infertile adults and prepubertal boys with testicular failure was performed. In the subgroups selected for this study, 55% of examined infertile women, 65% of infertile men and 64% of prepubertal boys with gonadal failure gave positive results by Western blotting with extracted sperm antigens. Sperm antigens with molecular weights of 57, 58, 62, 63 and 66 kDa were the most immunodominant entities recognized by antisperm antibodies from prepubertal boys. No positive reactions were detected by Western blotting in a control population of fertile adults, whereas in a group of prepubertal healthy boys only one sample revealed reactivity against sperm antigens of 58 and 70 kDa.