Freezing and thawing is thought to result in removal of spermatozoal membrane antigens. We investigated the presence of sperm antigens before and after freezing and thawing by means of the immunoperoxidase assay (IPAMA), sperm immobilization test (SIT), and separation of proteins by gel electrophoresis. The results of the IPAMA and SIT assays showed no difference in the membrane antigens before and after freezing and thawing. Analysis of surface proteins by gel electrophoresis demonstrated that freezing and thawing did not remove any particular group of proteins from the surface membrane of spermatozoa. According to the evidence of the three tests performed, there is no meaningful removal of antigens from the sperm cell surface membrane by the process of freezing, preservation, and thawing when carried out by the specific methods used. This work does not support the suggestion that in cases of immunologic incompatibility between spermatozoa and cervical mucus it would be possible to overcome the couple's infertility by employing the process of freezing, preservation, and thawing.