Pistachio psylla, Agonoscena pistaciae Burckhardt & Lauterer, is a key pest of pistachio trees in the pistachio-producing regions throughout Iran. The investigation of biology of pests under the field condition in each region is the first step that must be taken in developing an integrated pest management program. The seasonal fluctuations of eggs, nymphs and adults of pistachio psylla were investigated in 2007 and 2008. Results indicated that, the pest bears six complete along with one incomplete generation in Rafsanjan region. The mean generation period for adults, eggs and nymphs, from first to the sixth generation during 2007 and 2008 were assessed as 27.8±5.2, 27.4±2.6 and 27.1±1.9 days, respectively. The effect of canopy height on the distribution of eggs and nymphs, in the low, medium and high height conditions revealed that the density of eggs and nymphs increase with increase in the canopy height.