Interpretation of Shuttle Imaging Radar (SIR) images during the November 1981 flight of Columbia led to the idea that a palaeodrainage system of regional and perhaps transcontinental proportions crossed southern Egypt and northern Sudan prior to the onset of Quaternary aridity. Three seasons of field investigations in two locales (Wadi Arid and Wadi Safsaf, some 70-80 km apart) near the Sudan border of southern Egypt confirmed initial interpretations of the radar images and produced geologic evidence of fluvial deposition in broad radar river' valleys (designated RR-1) whose presence is now obscured by eolian sand sheets. Development of an integrated, regional river system probably occurred in the late Palaeogene or early Neogene. The river courses eventually were disrupted by tectonism, volcanism, and stream piracy. Their broad valleys were almost fully aggraded long before the middle Pleistocene appearance of man in the area. Some of the large palaeovalleys on the radar images contain narrow (0.05-2.0 km wide), braided inset channels (designated RR-2). The RR-2 channels, are believed to represent the last episodes of running water in the valleys during the Quaternary pluvials. The accumulated data support a provisional archaeo-geochronological framework for the last half-million years in the Wadi Arid-Wadi Safsaf area. This framework provides a new geomorphic explanation for the widespread distribution of buried and exposed middle Acheulian and late Acheulian assemblages. The interpretation emphasizes the importance of exploring the non-oasis zones for their archaeological and geochronological potential. This research demonstrates the potential of radar imaging for defining ancient drainage patterns in arid regions and their associated habitats for human occupation.