The insecticidal efficacy of mixtures of acrinathrin (pyrethroid) with carbamate fungicides (propamocarb, carbendazim, iprovalicarb, and diethofencarb) and insecticides (carbaryl, thiodicarb, pirimicarb, and oxamyl) was studied in a field strain of Frankliniella occidentalis (Pergande). The fungicide propamocarb and the insecticides pirimicarb and oxamyl were selected for further studies of their synergism action with more detailed bioassays. The method consisted of combining increasing concentrations of acrinathrin with a constant sublethal rate of the carbamate as synergist. These three carbamates did not show synergism to acrinathrin in a laboratory insecticide-susceptible strain, but they did in two field strains, with higher acrinathrin resistance corresponding to higher synergism. Carbamates such as pirimicarb, oxamyl, and propamocarb could be practical candidates for field use as synergists, even against other pests with metabolic resistance.