Abstract: The primary goal of all semen analyses is to accurately determine the fertilizing potential of semen samples rapidly.Since a spermatozoon must possess many attributes in order to fertilize an oocyte,the only way that we can more precisely predict the fertility is to develop unbiased assays that measure several sperm traits simultaneously.Conventional laboratory assays of spermatozoa,using subjective method,many are time consuming,and are necessarily conducted on samples of relatively small size,fall short of predicting the sperm function.Flow cytometry (FCM) permits us to objectively measure thousands of sperm for multiple characteristics in a short time with minimum preparation.The applications of FCM to evaluation of semen quality including sperm plasma membrane integrity,acrosome status,chromatin structure,mitochondrial activity as well as apoptosis etc,provide us valuable information regarding sperm function.FCM offers powerful tools and exciting opportunities for improving our ability to accurately evaluate semen quality with new fluorescent probes and techniques continuously being developed.