Aim: To explore the possible mechanisms of male infertility caused by antisperm antibody (AsAb). Methods: Thesoluble interleukin-2 receptor (sIL-2R) level in serum was analyzed by ELISA and Na~+ -K~+ -exchanging ATPase activi-ty in semen by phosphorus (Pi) assay. Results: The slL-2R level in serum was significantly higher and the Na~+ -K~+ -exchanging ATPase activity in semen significantly lower in AsAb positive infertile men when compared with thecontrols. Conclusion: The AsAb titer varies with the slL-2R level in serum. A decrease in Na~+ -K~+ -exchangingATPase activity in semen may play a role in male infertility caused by AsAb. Aim: To explore the possible mechanisms of male infertility caused by antisperm antibody (AsAb). Methods: The soluble interleukin-2 receptor (sIL-2R) level in serum was analyzed by ELISA and Na ~ + -K ~ +exchanging ATPase activi- ty in semen by phosphorus (Pi) assay. Results: The slL-2R level in serum was significantly higher and the Na ~ + -K ~ + -exchanging ATPase activity in semen significantly lower in AsAb positive infertile men when compared with the controls. Conclusion : The AsAb titer varies with the slL-2R level in serum. A decrease in Na ~ + -K ~ + -exchanging ATPase activity in semen may play a role in male infertility caused by AsAb.