The common pistachio psyllid, Agonoscena pistaciae Burckhardt and Lauterer, is a serious insect pest of pistachio trees where both adults and nymphs suck leaf sap. Their feeding causes reduced plant growth, falling of fruit buds and consequently poor yield. A. Pistaciae is a high potential for development of resistance to insecticides due to its short life cycle along with high potential for reproduction. In this study the susceptibility of A. pistaciae to amitraz and imidaclopride were tested under laboratory conditions. Nine A. pistaciae populations namely: Rafsanjan, Anar, Bam, Kerman, Shahrbabak, Sirjan, Heart, Pariz, and Paghaleh County were collected from pistachio orchards. Insecticide toxicity was evaluated through dip bioassay using technical insecticides up to 5th instar nymphs. Bioassay results revealed that these populations were of varied levels of  susceptibility to the pesticides, in a way that the lowest vs. the highest LC₅₀ values for amitraz and imidaclopride were determined, in the Bam (13.9 & 17.1 mg L^-1) and in Rafsanjan (310.5 & 46.3 mg L^-1) populations, respectively. From among the field collected populations, the highest levels of resistance to amitraz (22.3-fold) and to imidaclopride (2.7-fold) pesticides were detected for the Rafsanjan population. Glutathione     s-transferase gel activity was evaluated through a comparison of gel electrophoresis profile among populations. Based on band pattern, some differences were observed in band concentration and the relative mobility between Rafsanjan and Bam (susceptible) populations.