Evidence from sedimentary deposits and their biogenic com- ponent shows that aridity on the west coastal margins of southern Africa, south of 170S, was established during the late Cenozoic. The parallel evolution of aridity in Australia suggests that the climatic changes were global. Age corre- lation relates these events to the history of the Southern Ocean and the Antarctic ice cap. In the Miocene, the vertebrate fauna was of a pan-African nature and the environment sclerophyllous woodland and grassland with summer rainfall. Middle to late Miocene molluscs with a low degree of latitudinal organization of species show that the coastal waters were undifferentiated. Extensive phos- phorites indicate the existence of upwelling and a related subtropical anticyclone. The earliest evidence of the modern semi-arid environment and winter rain- fall in the southwestern Cape dates to the Pliocene. Invertebrate and vertebrate faunas show strong provinciality. Molluscs are indicative of cold upwelling off- shore south of latitude 32?S; pollens are partly sclerophyllous fynbos (macchia) suggesting a trend towards winter rainfall. Full semi-arid conditions with winter rainfall were achieved in the southwest by the end-Pliocene or earliest Pleisto- cene. Vertebrate faunas of that age were predominantly of a browsing type. Aridity in southern Africa was thus fully established in the Quaternary, but was affected by global climatic oscillations. Laterally-restricted late Pleistocene warm (hyperthermal) mollusc assemblages suggest a warm hydroclimate in the numerous lagoons and estuaries created by a marine transgression during a thermal maximum 120000 years ago. A southward shift of the subtropical anticyclone and zone of upwelling is inferred. Evaporite deposits indicate arid conditions and a poleward contraction of the rain-bearing westerly flow. Conversely, in the succeeding cold interval (hypothermal) there was a 50