Seed proteins of seven taxa of Acer native to eastern North America were obtained by extraction in 2.5% saline buffer, pH 7.0. These were investigated using the techniques of polyacrylamide disc electrophoresis, immunoelectrophoresis, and double diffusion. Groupings indicated by our protein data were compared with groupings by other researchers based on morphological data. The members of the section Saccharina, A. saccharum subsp. saccharum, A. s. subsp. nigrum and A. s. subsp. floridanum, were found to have close protein similarity. A. negundo, thought by several workers to be the most distinct of the maples, was found to have relatively high protein similarity with the members of the section Saccharina. A. rubrum and A. spicatum were shown to have the least protein similarity to the other taxa investigated. There is low protein similarity between these two taxa, however, indicating they are divergent. The traditional placement of A. rubrum and A. saccharinum in the same section was supported by the relatively high protein similarity of these taxa. Data obtained by serological techniques and polyacrylamide disc electrophoresis were found to be complementary. However, polyacrylamide disc electrophoresis was more sensitive in detecting the protein differences among the taxa investigated.