The Pedirka is a Permian infrabasin beneath the western Great Artesian Basin. It lies mainly in the central north of South Australia and the southeast of the Northern Territory but a small part may also extend into Queensland. Much of the eastern Pedirka Basin underlies the Simpson Desert. The whole of the basin has been covered by aeromagnetic and gravity surveys which, in conjunction with the results of seismic work and exploration drilling, have revealed the existence of two major subdivisions within the basin. The roughly north-south McDills Trend separates an area of thick Lower Palaeozoic sediments in the west from an area of thin Lower Palaeozoic but thicker Permian and Mesozoic sediments to the east.thicker Permian and Mesozoic sediments to the east. The Pedirka Basin displays a maximum development of the Permian to the east of the wells drilled. The glacigene sediments of the Crown Point Formation are present over wide areas of the basin. The overlying Purni Formation is less widespread but, where present; the sands, shales and coals may be well over 300 m in their thickest developments. The lithology of the Purni Formation is similar to that of the gas-bearing formations of the Cooper Basin and structures suitable for trapping hydrocarbons are developed in the Permian in the eastern Pedirka Basin. A Triassic caprock could be present in this region.The western sub-basin, beneath the Pedirka Basin, contains large thicknesses of Lower Palaeozoic and possibly Proterozoic sediments. Sedimentation in this area may have been continuous with that in the Amadeus Basin during parts of the Palaeozoic. Cambrian carbonates and shales, Ordovician sands and Devonian terrestrial sands, shales and conglomerates have been reported from some of the wells. Several formations are considered to contain as much, hydrocarbon potential as the Permian rocks. Mesozoic strata unconformably overlie all Palaeozoic rocks in the area. The Mesozoic sediments increase in thickness in an easterly direction. The whole region was affected by the. Alice Springs Orogeny which developed generally gentle structures in the pre-Permian strata and caused syndepositional movements during the Permian. Six petroleum exploration wells have been drilled to date. No shows of hydrocarbons were encountered but large areas of the Pedirka Basin remain to be explored and several interesting structures which have been outlined remain untested to date.