Adult lygus bugs, Lygus hesperus (Knight), were collected from alfalfa fields in 11 different cotton-producing areas of Arizona. A standardized, glass vial method was used to estimate susceptibility of the collected populations to the organophosphate insecticide, acephate (Orthene®), and the pyrethroid, bifen-thrin (Capture®). Overall, lygus from throughout the state were significantly less susceptible to acephate and bifenthrin in 1995, than in 1994. Resistance of lygus to acephate continues to be widespread, and intense, but not uniform in Arizona. In 1995, all populations possessed individuals capable of surviving exposure to vial treatments of 10,000 (g/ml acephate. Lygus bugs from Safford and Maricopa represented the most and least susceptible populations, respectively, to both acephate and bifenthrin. These two popula-tions were tested for susceptibility to the following nine other insecticides: aldicarb (Temik®), dimethoate (Gowan Dimethoate E267®), endosulfan (Gowan Endosulfan 3EC®), imidacloprid (Admire 2F®), malathion (Gowan Malathion 8®), methamidophos (Monitor 4®), methomyl (Lannate LV®), oxamyl (Vydate 3.77L®), and oxydemeton-methyl (Metasystox-R SC®). The Maricopa population was significantly less susceptible to six of these insecticides. Our findings support the hypothesis that the intensive use of pyrethroid and organophosphate insecticides for whitefly control in cotton has selected for resistance in lygus. This result portends increased problems with lygus control in the future, points to the need for developing new tools for controlling lygus bugs in Arizona cotton, and underscores the urgent need to find alternatives to the current heavy reliance on insecticides for managing whiteflies in cotton.