Sweep net samples were taken at weekly intervals in forty fields in Maricopa Co., Arizona, at two locations to determine if early season ultra low volume (ULV) malathion treatments were influencing pest or beneficial arthropod populations. One half of the samples were taken in untreated fields. There was no significant difference in whitefly populations between the two treatments at either location. There were significantly more thrips species in the treated fields for most of the sample dates. Aphids were significantly greater in the treated fields at Gilbert in the 2nd wk and at Laveen on the third week after the malathion treatments. Lygus spp. and cotton fleahoppers combined were significantly greater in the untreated fields during the 1st and 2nd weeks following the malathion treatments at both locations. Total beneficials were significantly greater in the untreated fields on the 1st week after malathion treatment but not for the following week. Orius spp., Geocoris spp., and spiders were the most abundant predators. Orius spp. and spiders were not affected by the malathion treatment. Orius spp. populations were greater in the treated fields during the 2nd and 3rd weeks after treatment, but spider populations did not change in relation to the treatment. Geocoris spp. were negatively impacted by the malathion treatments, and there were significantly more in the untreated fields at Laveen on the 2nd and 3rd wk after the malathion treatments.