This paper examines the biogeography of cultivars belonging to the domesticated potatoes S. stenotomum Juz. et Buk., S. goniocalyx Juz. et Buk., S. x chaucha Juz. et Buk., and S. tuberosum subsp. andigena Juz. et Buk. It describes the spatial patterning of cultivars in a highland region of Southern Peru and evaluates physicalenvironmental (climate, soils) and human-geographic (seed selection, seed exchange) explanations for observed distributions along elevational gradients and among areas. Results of field sampling, soils and climate analysis, a factorial experiment, interviews with farmers, and ethnographic participant observation indicate that diverse conspecific cultivars of native potato species are not distributed in fine-grained elevational microenvironments but rather are clustered in geographic micro-regions (or so-called cultivar regions). The concentration of cultivars with endemic distributions in areal clusters is shaped primarily by seed-exchange networks. Environmental factors and the selection of seed by agriculturalists do not significantly differentiate the spatial patterning of conspecific native-potato cultivars along either elevational or areal axes. Evaluation of the major pressures moulding the distribution of cultivars and the geographic scale of their spatial patterning forms an important preliminary step for planning the in situ conservation of genetically diverse native