The present study was designed to test the validity of the semen analysis(S/A) and the sperm penetration assay(SPA) as a prognostic indicator of male fertility in 123 patients undergoing in vitro fertilization(IVF). We attempted to correlate the traditional semen parameters or the extent of sperm penetration in SPA with the results of human IVF rate or cleavage rate. Poor correlation was found between the results of S/A and human IVF rate(sensitivity, 80.6% ;specificity, 46.7%; positive predictive value, 91.6%;negative predictive value, 25%). Conversely, good correlation was found between the results of SPA and human IVF rate(sensitivity, 100% ; specificity, 80% ;positive predictive value, 97.3% ;negative predictive value, 100%). Our results corroborate the conclusion that SPA can be a valuable tool as a prognostic indicator of male fertilizing ability.