Gel electrophoresis in sodium dodecyl sulfate and gel filtration in guanidine. HCl indicate that native concanavalin A contains several molecular species. An intact subunit of molecular weight 27,000 has been purified from this mixture. In addition, three fragments of the intact subunit have been isolated and characterized. A working model of the concanavalin A molecule has been constructed based on pairings of the intact subunit and of subunits consisting of fragments.