ABSTRACT Kosteletzkya pentacarpos (L.) Ledeb. (syn. 5 Kosteletzkya virginica (L.) C. Presl ex A. Gray) has been treated as a single variable species or as a species including four varieties: K. virginica var. althaeifolia, var. aquilonia, var. smilacifolia, and var. virginica. The aim of this study was to test the validity of formally recognizing these putative infraspecific taxa with a statistical analysis of morphological data. Loans were received from 15 herbaria, for 1,114 specimens; 224 were selected. Measurements were taken from these 224 specimens for 42 characters and analyzed by canonical discriminant analysis, which recognized two dimensions. Var. smilacifolia and var. aquilonia were separated from the other two groupings and correctly predicted at 100%. Var. smilacifolia is morphologically distinct from the other taxa in having linear hastate leaves with reflexed linear lobes, an unbranched inflorescence, a slender stem, and a mostly entire leaf margin. A new combination is proposed: Kosteletzkya pentacarpos (L.) Ledeb. var. smilacifolia (Chapm.) S.N. Alexander. All other former putative infraspecific taxa are synonymous with Kosteletzkya pentacarpos var. pentacarpos.