A first step in the characterization of cellular functions is the identification of the proteins involved. The spermatozoon is an accessible cell that is particularly suited for analysis and indeed it was one of the first cells from which proteins were identified. An important advance in the identification of the protein composition of the spermatozoa was accomplished in the past using electrophoresis separation methods and protein sequencing with the Edmman procedure. However the recent developments in mass spectrometry have boosted the potential for the identification and study of sperm proteins. Catalogs of thousands of spermatozoan proteins in human and in model species are becoming available setting up the basis for subsequent research, diagnostic applications and development of specific treatments. The present article reviews the available scientific publications dealing with the composition and function of the sperm cell using a mass spectrometry proteomic approach.