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The pistachio (Pistacia vera L.) requires extended dry summers for its proper development and productivity. These conditions are characteristic of arid and semiarid areas, as are mild winters which are more constant due in part to climate change. Under these conditions chilling requirements for the optimum budbreak of this species are not met. Therefore, the use of chilling compensators is one of the ways to solve this problem. This experiment was carried out to evaluate the effects of hydrogen cyanamide on budbreak in pistachio (Pistacia vera L.) grown in an arid region with insufficient chilling hours (<= 7.2 degrees C). Dormant buds on branches from 1 to five years old were treated on February 20 of both 2006 and 2007 with 0, 25.5 and 51.0 g.L(-1) of H2CN2 [hereafter referred to as 0, 2.5 and 5.0 % (v/v) H2CN2]. Hydrogen cyanamide advanced and increased vegetative budbreak in branches from one to five years old. The highest budbreak was observed when H2CN2 was applied at 5.0 % without causing phytotoxicity. Hydrogen cyanamide applied at 5.0 % 30 days before expected budbreak can increase budbreak and substitute for chilling when pistachio is grown in environments with mild winters.