This review proposes a sequence of events of the acrosome exocytosis in mammalian spermatozoa that is similar to the regulated secretion pathway in somatic cells. During sperm transit through the female reproductive tract, extracellular agonists meet and bind to receptors on the sperm`s plasma membrane activating one or more intracellular proteins mediated by either calcium binding or phosphorylation (dephosphorylation) or both. The activated protein(s) continue the transduction cascade(s) that ultimately results in the acrosome reaction.