Hyaluronic Acid (HyaluronicAcid-HA) is one of the major components of the extra cellular matrix of the egg (ECM) matrix and plays a critical role in sperm selection: mature spermatozoa possess a membrane glycoprotein that has a domain for hyaluronidase activity : PH20. The PH20 protein is bifunctional: prior to the acrosome reaction it has hyaluronic acid activity (thus degrading the Hylauronic Acid and allowing penetration of the ECM), after the acrosome reaction it is involved in the secondary bond between the sperm and the zona pellucida of the oocyte. It has been shown that only mature spermatozoa are able to bind in vitro with Hyaluronic Acid (HA) and thus this bond indicates the completion of spermatogenesis. PVP, an artificial compound used in ICSI to reduce the motility of spermatozoa, can be replaced by HA which in itself is viscous.The best spermatozoa may be isolated since they attach to the HA. This modified ICSI is termed "PHYSIOLOGICAL ICSI" and is routinely performed in our centre.