It has been over a hundred years since the first description of fertilization. Contact between sperm and egg plasma membranes results in binding that is soon followed by membrane fusion. Only recently has progress been made in the identification of the surface molecules of mammalian gametes that are involved in sperm-egg binding and fusion. This review covers the processes that lead up to the joining of the plasma membranes that surround these two cells, including the complex development and maturation of both sperm and eggs and also the events of sperm-egg membrane binding and fusion. The involvement of the sperm protein PH-30 and other candidate sperm membrane proteins in this process is discussed, as well as the possibility that egg integrins are responsible for sperm binding.