Abstract
The sperm penetration assay, or zona-free hamster oocyte penetration assay, is utilized to measure the ability of sperm to undergo capacitation, fuse with the egg membrane, and decondense the sperm head within the cytoplasm of the oocyte, resulting in the formation of the male pronucleus. The test is scored by calculation of the percentage of ova that are penetrated (the original assay developed) or the average number of sperm penetrations per ovum (the sperm capacitation index of the optimized assay). The sperm penetration assay identifies those couples that will have a high likelihood of success with in vitro fertilization.