A monoclonal antibody 2F7.C7 which identifies an epidermal antigen common to both anuran and urodele amphibia is described. This antigen has a high molecular weight and is expressed at stage 12 1/2 first inside and then on the surface of epidermal cells. It is not expressed on presumptive nervous tissue. It is expressed on all cells of the larval epidermis including ciliated and nonciliated cells and sucker. The relationship of the epidermal antigen to 'epimucin' is investigated by blocking experiments using Peanut agglutinin. These studies suggest that either the molecule recognized by 2F7.C7 is not epimucin, or that its epitope is far away from the lectin-binding site. Studies using this antibody in grafting and sandwich experiments are discussed and an overall scheme of epidermal development in Xenopus is presented.