Objective: Apoptosis appears to have an essential role in the control of testis germ cell number and Fas-mediated apoptotic pathway has been implicated in controlling apoptosis during spermatogenesis in a number of mammalian species .The apoptotic marker Fas was detected in ejaculated sperm with a higher incidence of Fas positivity in infertile men. In this study each sample was analyzed for expression of Fas by Flowcytometry. Sperm shows Fas positive but PI negative (early apoptotic) Lysis was activated by antibody-antigen complexes via Fas receptor and Complement. Materials and Methods: Semen samples were obtained from 73 patients referring to Isfahan Fertility and Infertility Center . To Complement mediated lysis each samples treated with 5μl Purified Mouse Anti-Human CD95 mAb and then the cells incubated for 1 hour at 37 ºC with 25 μl Rabbit complement To demonstrate the effect of complement-activating and the degree of cell lysis PI was used. Results: Fas expressions of sperm in subfertile individuals were much lower and with a mean of 4.1%. No significant difference in percentage PI was detected before and after activation of classical pathway (p = 0.53). Conclusion: No significant differences in percentage of PI was detected before and after activation of complement classic pathway. Therefore this may conclude that Fas system or possibly abortive apoptosis is likely none functional.