During the first half of the present century, scholars such as Reichard and Kluckhohn took it for granted that Navajo society was thoroughly matrilineal with respect to inheritance and corporate groups larger than the coresident extended family. In recent years, however, the pervasiveness of matrilineality has been questioned by a number of scholars, most notably Lamphere and Adams. Only Aberle has continued to view matrilineal principles as central to Navajo social organization and has attempted to reconcile the differing interpretations. The present paper presents synchronic and diachronic data from three diverse areas of the Navajo Reservation: (1) the open range of the Kaibeto Plateau, (2) the confined valley rangeland of Kitsili on Black Mesa, and (3) the restricted farmland of Canyons de Chelly and del Muerto. We find that matrilocal residence, matrilineal inheritance of key resources, and resident matrilineages that control, manage, and defend these resources are found in those areas where conditions are closest to those prevailing in the prereservation periods