Calcretes are associated with many sites of archaeological or palaeontological interest in southern Africa and have long interested Quaternary workers, pro- bably mainly on account of their possible palaeo- climatic implications. These materials are still not fully understood however, and it is the purpose of this paper to illustrate some of the basic types and to attempt to deduce something about the conditions under which they formed. There are many different types of calcretes, and as they have not previously been fully described or defined and as a comprehensive work on their detailed classification is being prepared for publication elsewhere, only the most useful types from the interpretation point of view will be selected for discussion here. The types dealt with are nodular calcretes, calcified gravels and sands, hardpan cal- cretes and boulder calcretes, and have been briefly described by Netterberg (1967).