The fate of agricultural biodiversity varies among the native crops produced in a mountainous region. Four native crops (potatoes, maize, ulluco, quinoa) cultivated in the southern Peruvian sierra demonstrate different patterns of cultivar loss and cultivar maintenance. Contingent social, economic and environmental conditions in mountain agriculture shape the distinct fates befalling the cultivars in each crop. Three sets of specific conditions contribute to differences in the patterning of cultivar loss and maintenance: (1) proximate conditions in the local peasant economy, particularly access among agricultural households to land, labor, and capital, and changes in the availability and quality of the three endowments; (2) the social and cultural value of the crop in the local diet and cuisine; and (3) the biogeographic patterning of cultivars. Maintenance of cultivars currently marks the ulluco and quinoa crop as well as many potato and maize types. Cultivar loss besets the fastmaturing potato S. phureja and the slow-maturing maize types. To incorporate variable in situ crop-conservation programs into development planning for montane regions requires thoroughly assessing the contingent conditions for continued production."The post-modern era has moved from genetic erosion to genetic wipe-out" (Harlan 1972: 214) "Genetic diversity in crops continues in many environments, but its continuity is particularly marked in mountain areas" (Brush 1986: 153)