Objective To investigate the role of circulating antisperm antibody (ASA) in the pathogenesis of endometriosis-associated infertility.Methods Serum samples were collected from 75 infertile women with minimal or mild endometriosis.Indirect immunobead test reporting on the percentage of motile sperm with adherent immunobeads was used to detect the circulating ASA levels.Results No infertile cases enrolled in the present study developed significant ASA level in the serum samples.That is to say,no one could achieve the diagnosis of ASA- mediated infertility according to the World Health Organization criteria (50％ or more of the motile sperm with immunobead binding).There were only 5 cases (6.7％) who had 20％-40％ of the motile sperm that were found to have adherent particles of ASA-IgG.All the cases were found to be completely absent of ASA-IgA.Conclusion Endometriosis seems to have little impact on the production of circulating ASA.Clearly,ASA is not the key factor implicated in the pathogenesis of endometriosis-associated infertility.The presence of a low titer of ASA in a small proportion of the infertile women with endometriosis may exist by chance and,at least in part,explain the impaired fecundity in those patients.