Hot deserts are characterized by low mean annual rainfall (<250 mm, <10″) and very high evapotranspiration, so karst processes are inhibited. However, karst features are abundant and well developed in many deserts around the world. Salt caves occur predominantly in this environment and develop rapidly despite the arid climate, because they are formed mainly by rare, but intense, rain events. Deserts also preserve, relatively unaltered, gypsum and carbonate karst that formed in prior wetter climates or by hypogene processes. Carbonate karst, which is the most common karst in hot deserts, is modified very slowly by desert processes, including dissolution and salt crystallization, which fragments bedrock and speleothems. Keywords: Aridity, Carbonate karst, Deserts, Evaporite karst, Evapotranspiration, Gypsum, Halite, Limestone, Rainfall, Salt, Salt weathering.