Proteins and six enzymes (esterase, peroxidase, catalase, leucine aminopeptidase, alcohol dehydrogenase, achromatic oxidase) in individual seeds from 36 species and collections of Arachis were characterized by using polyacrylamide and starch gel electrophoretic techniques. These data were used to evaluate the biosystematics of Arachis. Support was found for the thesis that each wild relative of the cultivated peanut, Arachis hypogaea L., has been properly classified into coherent groups of species under the following taxonomic sections: Axonomorphae, Erectoides, Caulorhizae, Rhizomatosae, Extranervosae, Pseudoaxonomorphae and Triseminalae. For example, the mobility of most bands in the gel patterns of proteins and enzymes of A. hypogaea coincided very closely with those of the wild species, A. monticola PI 219824, supporting studies which have shown that these two species are closely related and should be classified together. The Similarity Index method, based upon the percent of protein and enzyme bands with similar and dissimilar mobilities compared among gels of seeds of species and collections, produced s-values that further supported the taxonomy of this genus as it is known today.