Fertilisation is a highly programmed process by which two radicallydifferent cells, sperm and egg, unite to form a zygote, a cell with somaticchromosome numbers. Development of the zygote begins immediately aftersperm and egg haploid pronuclei come together, pooling their chromosomesto form a single diploid nucleus with the parental genes. Mammalianfertilisation is the net result of a complex set of molecular eventswhich allow the capacitated spermatozoa to recognise and bind to theegg's extracellular coat, the zona pellucida (ZP), undergo the acrosomereaction, and fuse with the egg plasma membrane. Sperm-zona (egg)interaction leading to fertilisation is a species-specificcarbohydrate-mediated event which depends on glycan-recognising proteins(glycosyltransferases/glycosidases/lectin-like molecules) on sperm plasmamembrane (receptors) and their complementary glycan units (ligands) onZP. The receptor-ligand interaction event initiates a signal transductionpathway resulting in the exocytosis of acrosomal contents. The hydrolyticaction of the sperm glycohydrolases and proteases released at the site ofsperm-egg interaction, along with the enhanced thrust generated by thehyperactivated beat pattern of the bound spermatozoon, are importantfactors regulating the penetration of egg investments. This review focuseson sperm molecules believed to be important for the interaction with thefemale genital tract, passage through cumulus oophorus and attachment toZP, induction of the acrosome reaction, secondary binding events, andpassage through the ZP. An understanding of the expression and modificationsof molecules thought to be important in multiple events leading tofertilisation will allow new strategies to block these modifications andalter sperm function.