One of the most charismatic American plant families, the Cactaceae, is well represented in Chile. Biogeographic analysis of the Chilean representatives is rarely undertaken, mainly due to the complex taxonomy of the group. Taking account of the most recent taxonomic treatments and distributional knowledge, an attempt is made here to develop a biogeographic regionalization by means of parsimony analysis of endemism (PAE) and the program NDM/VNDM. The first method yields three areas of endemism in northern Chile bordering the Atacama Desert to the North and to the South, and the second method yields one area which includes North-Central Chile. Advantages and restrictions of the methods are discussed. Finally, the evolution of the family is discussed in relation to the rise of the Atacama Desert and the systematic interpretation of the group "Cacti have a special fascination all of their own. Like the brilliantly colored hummingbirds, the Cactaceae are creatures of the New World" (Barthlott 2001, p 9). With representatives ranging from minute spiny dwarf cacti of a couple centimetres in diameter to the majestic columns of the Arizona giant saguaro, the Cactaceae is the second largest family of angiosperms almost exclusively restricted to the New World. The richest American plant family is Bromeliaceae; both families have one taxon occurring outside America: the Bromeliaceae has Pitcairnia as a native genus in West Africa; the Cactaceae has Rhipsalis wider distributed in Africa, Madagascar, Mauritius, the Seychelles and Ceylon. The family is present in America from central Canada to Patagonia. The highest diversity is found in the arid environments of North and South America, but contrary to the popular believe due to their spiny morphology, the family is not strictly restricted to arid environments: it also occupies temperate, sub-tropical, and tropical environments reaching rnesic southern Chile and Argentina and ranging from the coast to the high Andes (Kraus 1995; Mauseth et al. 2002). The southern limit for the family is the Santa Cruz province in Argentina (ca. 50 degrees S, Anderson 2001), where Austrocactus, Gymnocalycium, Maihuenia, Maihueniopsis, and Pterocactus occur.