Two major palaeodrainage systems of Tertiary age, with watersheds of up to 35 000 square km and channel lengths of 200-250 km, have been recognised and delineated using LANDSAT imagery, during 1:250 000 scale geological mapping in western South Australia. These systems have been termed the Tallaringa Palaeodrainage System and Mirackina Palaeochannel. The former is largely intact and still forms a subtle valley, appearing as a pale-toned, branching feature on satellite imagery. The channel-fill of the latter has been silicified and ferruginised, and through erosion has been exhumed, to form, today, a duricrust capping to an isolated, sinuous line of mesas. It is prominent as a dark feature on the imagery due to the ferruginisation. LANDSAT imagery, reconnaissance-geological and barometric altitude data has been subsequently used to develop a preliminary interpretation of Tertiary palaeodrainage throughout western South Australia, and of Tertiary palaeogeography on the north-eastern margin of the Eucla Basin. The systems are of economic interest: they are potentially useful aquifers and hosts to heavy mineral placer deposits; contain large volumes of low-grade lignite and medium-grade palygorskite-type clays; and contain sediments which are lithologically similar and stratigraphically equivalent to channel-confined hosts to economic uranium mineralisation both at Lake Frome and Yeelirrie. While the two palaeodrainage systems described in detail have been eroded and/or leached to a greater or lesser degree, they serve to indicate the possible sediment content and consequent mineral potential of other systems in the region. The definition of palaeodrainage patterns will therefore be prerequisite to assessing the overall mineral potential of the province and to primary geological mapping of the region. The use of LANDSAT imagery and complementary techniques for this purpose has been demonstrated, and it is clear that it will be an important tool for ensuring the success of such programmes in the future.