Aim: To investigate a simple method for assaying acrosin activity for the evaluation of male fertility. Methods:The acrosin activity of 7.5 × 10~6 sperm without seminal plasma and acrosin activity inhibitors was assayed using N-α-benzoyl-DL-arginine-p-nitroanilide (BAPNA) and detergent (Triton X-100) as substrate. Results: The acrosin ac-tivity of 60 normal fertile men (35 ± 10 μIU/10~6 sperm ) was higher than that of 168 infertile men ( 16 ± 8 μIU/10~6sperm) (P <0.01). It was indicated that there was a significant positive correlation between the acrosin activity andthe sperm motility ( r ≥ 0.6534, P < 0.01) and a significant negative correlation between the sperm malformed rateand the WBC number ( r ≤ -0.5426, P < 0.01). The temperature and time of incubation and the sperm concentrationcould influence the assay results. Conclusion: Acrosin activity is an important index for the evaluation of male fer-tility. The approach developed by the authors is a simple method for the determination of acro Methods: The acrosin activity of 7.5 × 10 ~ 6 sperm without seminal plasma and acrosin activity inhibitors was assayed using N-α-benzoyl-DL-arginine- Results: The acrosin ac-tivity of 60 normal fertile men (35 ± 10 μIU / 10 ~ 6 sperm) was higher than that of 168 infertile men (16 It was indicated that there was a significant positive correlation between the acrosin activity and the sperm motility (r ≥ 0.6534, P <0.01) and a significant negative correlation between the sperm malformed rate and the temperature and time of incubation and the sperm concentration of due to the assay results. Conclusion: Acrosin activity is an important index for the evaluation of male fer-tility. The approach developed by the authors is a simple method for the d etermination of acro