Current taxonomic interpretations of Solanum microdontum BITTER partition the species into two or three infraspecific taxa, variously recognized as subspecies or varieties. The present study reexamines these taxa using morphological data from four individuals each of 69 accessions from most of the range of the species, planted in a common field plot. Our results show that the character states used to recognize infraspecific taxa in S. microdontum often vary within accessions and have no correlation with geography. We conclude that past hypotheses have used typological concepts and that infraspecific taxa are not warranted. This study questions other hypotheses of infraspecific taxa in sect. Petota. Solanum microdontum BITTER is a highly variable species distributed from northern Bolivia (La Paz Prov.) to northwestern Argentina (La Rioja Prov.). It is a member of sect. Petota, a group of 232 species (as interpreted by HAWKES 1990) related to the cultivated potato. The species is self-incompatible and diploid (2n = 2x = 24), except for some scattered triploid cytotypes in the southern part of the range in Argentina (OKADA 1981). Many populations of S. microdontum are distinguished by entire leaves, but intra- and interpopulational variability encompasses morpho- types with pinnately-dissected leaves more similar to those of other wild species. This variability has been partitioned into six species, three subspecies, and six varieties, but current classifications reduce this variability to one species with two subspecies: subsp, microdontum and subsp, gigantophyllum (BITTER) HAWKES & HJERT. (HAWKES 1990; Table 1) or three varieties, vat. microdontum, var. metrio- phyllum BITTER, and var. montepuncoense OCHOA (OCHOA 1990). Var. microdontum and var. metriophyllum are equivalent nomenclaturally to subsp, mierodontum and subsp, gigantophyllum, respectively; var. montepuncoense is distinct, and is a possible interspecific hybrid (see below). This study investigates the morphological and geographical patterns of variability in S. microdontum to find if infraspecific taxa are warranted.