The Middle Kalahari of north-central Botswana is dominated by a huge basin of inland drainage partly filled with the geological formation known as the Kalahari beds, of late Tertiary to Recent age and of aeolian, lacustrine, and fluviatile origin. The landforms appear to have evolved in a climatic environment oscillating between wetter and drier episodes leaving a legacy of humid and arid landform relics in close juxtaposition with active contemporary forms, while downwarping and faulting appear to have greatly influenced their development. What appear to be structural troughs are occupied by the huge active terrestrial delta of the Okavango, and the vast playa-like complex of the Makgadikgadi pans, tenuously linked by the Boteti river. A large lake and a number of smaller lakes, all of fluctuating extent, seem to have occupied much of the area in the past. The mapping and study of the former shorelines of these lakes, and radio-carbon dating of the deposits associated with them may help to establish a chronological framework for the geomorphological evolution of the area, which should in turn aid the stratigraphical ordering and understanding of the succession of the Kalahari beds. Considerable light may also be thrown on the evolution of the Zambezi and Limpopo drainages from the late Tertiary to the mid-Pleistocene. Orange river in the south, into the Zaire basin in the north, and which is probably, according to Wellington, the largest continuous expanse of sand-covered surface in the world. The area comprises the end drainage basin of the Okavango river together with that of the Chobe, and the upper Zambezi which impinges in the extreme north, together with the whole of the depression occupied by the Makgadikgadi pans. The sand surface is continuous except for scattered outcrops of Pre-Cambrian and Karroo rocks, and the relief is slight, the range lying between 00ooo m which is the approximate bounding contour of the area, and a low point of 890 m in the north of Sua pan. The total area is about i6o ooo km2. It is a zone which is remarkable for the close juxtaposition of landforms which are primarily due to the action of water, and others which are entirely the result of arid climate processes, and both groups show examples which are in active process of development or are in a relict state. The whole area comprises a vast basin of internal drainage into which aeolian, fluviatile, and lacustrine sediments have been accumulating probably since late Cretaceous times. Four major rivers, the Cubango and Cuito (which unite into the Okavango), the Cuando (known in Botswana as the Chobe or Linyanti), and the upper Zambezi flow in parallel courses southwards from the Angolan highlands towards this basin. In the latitude i7 50o'S to I8'S these rivers turn eastwards, but then the Okavango and Cuando turn south again into Botswana, leaving only the