Determination of chilling and heat requirements of pistachio (Pistacia vera L.) cultivars is important for satisfactory growth and development, particularly when large-scale commercial production is desired. This experiment was conducted to determine chilling requirement inducing vegetative and flower buds of Kalle-Ghuchi, Owhadi, Ahmad-Ahgaei, and Akbari pistachio. Shoots with enough vegetative and flower buds were taken from pistachio trees during autumn 2007 and 2008 when temperature reached to≤15℃. Cuttings with flower buds were kept under (5±1)℃ for 0, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, and 1300 h, respectively, and cuttings with vegetative buds were kept at 51℃ until 1 500 h. The results indicated that pistachio eultivars requite chilling time between 750-1 400 h and heat requirements between 8 852-15 420 growing degree hours (GDH). Consequently, Kalle-Ghuehi had the lowest chilling (750-950 h), and heat (8 852-9 768 GDH) requirements, Ahmad-Aghaei and Owhadi had intermediate (1 000-1 250 h, 10 656-13 320 GDH) and Akbari had the highest chilling (1 200-1 400 h) and heat (11 863-15420 GDH) requirement.