This chapter reviews the germination behavior of desert species as an integral trait of a compounded strategy by which the plant adapts to arid environments. An analysis of germination of desert species within the complex pattern of plant adaptation to aridity is provided in this chapter. The climate in different regions of the world is determined mainly by the unequal latitudinal distribution of the solar irradiation reaching Earth's surface. Several main deserts of the world are located between regions with Mediterranean and semiarid tropical climates. Spatial variability of water availability in deserts occurs in both macro- and microscale. Mass germination in deserts occurs only after a threshold amount of precipitation (effective-rain) has fallen, provided that other limiting factors (mainly temperature) allow germination. Interactions between light and temperature may also determine the timing of germination in light-sensitive seeds. Many efforts have been devoted to the identification of the factors controlling seed germination of arid and semiarid species in vitro.