When zona-free hamster egg test is used for assessment of fertilizing ability in human spermatozoa and elucidating the mechanism of fertilization, it needs to know the effect of zonaless, polyspermic, and cross fertilization. In this study, it is shown to observe unusual fertilization and sperm head chromatin decondensation. Multiple flagella sperm was also shown to be capaole of penetrating egg. These observations seems to be very useful for electron microscopic observations.
