The cultivated peanut, Arachis hypogaea L., is a member of section Arachis nom. nud. along with its tetraploid progenitor, A. monticola Krap. et Rig., four validly described diploid species, eight diploid species whose names have never been validly published, and a large collection of taxa discovered since 1975. Systematic relationships and possible species circumscriptors are assessed in section Arachis by means of numerical taxonomy. Seventy-three accessions were grown in the field and three randomly selected specimens of each accession were evaluated. Numerical techniques in the form of cluster and principal components analyses were used on 56 characters, including 20 reproductive, 30 vegetative, and six created variables. Most variation was observed for leaflet size and shape, followed by branching habits and flower size. Although grouping of accessions did not always conform to expectations based on published species descriptions, general relationships among taxa are evident from the analyses. A total of 20 to 25 species will likely exist in section Arachis based on the observed variability.