Phospholipase A₂ (PLA₂), its localization on human sperm and its involvement in sperm‐egg interaction, was investigated. Sperm‐egg interaction was examined using an in vitro assay of the interaction between human sperm and zona‐free or zona‐intact hamster egg. PLA₂‐specific antibodies and/or lysophosphatidylcholine (LPC) were added to the coincubation medium. PLA₂ was localized on the anterior tip of the human sperm head by an immunogold silver staining method in light microscopy (IGSS) and TEM. PLA₂‐specific antibodies inhibited human sperm‐zona‐free oocyte fusion significantly. LPC treatment allows interspecies fertilization of zona‐intact hamster oocytes. PLA₂ plays an important role in membrane‐fusion events. This statement is supported by the fact that PLA₂ is localized in the region where an exocytotic event, such as the acrosome reaction, occurs in the spermatozoon. PLA₂‐specific antibodies inhibited sperm‐egg fusion, but not sperm‐oolemma adhesion. LPC may stimulate the fertilizing ability of spermatozoa and induce changes on the zona pellucida and on the oolemma promoting in sperm‐egg fusion. Based on these findings, it is suggested that sperm PLA₂ and one of its modulators, the LPC, may contribute to membrane‐fusion events in mammalian fertilization. J. Exp. Zool. 279:81–88, 1997. © 1997 Wiley‐Liss, Inc.