Polyclonal antibody of the boar sperminogen was used to characterize the boar sperm proteinase sperminogen. Boar sperminogen was purified from the acid extracts of the washed epididymal spermatozoa by gel filtration through a Sephadex G-100 column. followed by preparative SDS-PAGE. The sperminogen band was sliced out and was eluted from the gel matrix. The purified sperminogen was used to produce the polyclonal antibody of the boar sperminogen. When characterized on a Western blot, the final preparation of sperminogen appeared as a homogenous protein with a molecular weight of 32 kDa. The relative migration of sperminogen was distinctly different from the major components of the proacrosin-acrosin system as well as all the observable proacrosin activation by-products detected on the Western blot. The sperminogen antibody, however. cross-reacted with the proacrosin-acrosin system