ABSTRACT: Still under debate is the location in the genital tract where antisperm antibodies transuded from serum and locally produced antibodies, respectively, become attached to the surface of the spermatozoa. The mixed antiglobulin reaction (MAR) for immunoglobulin (Ig) G, IgA, and locally produced secretory IgA (sIgA) could be carried out on motile spermatozoa from epididymis from 13 of 34 men undergoing vasovasostomy. Four months and one year after the operation the MAR was repeated on a fresh semen sample from all patients. It was found that transuded as well as locally produced antisperm antibodies were bound to spermatozoa at the epididymal level of the genital tract. The follow-up results on semen were almost identical to the results obtained with epididymal spermatozoa.