The effects of three processing methods for corn and wheat samples on the stability of storedgrain protective insecticides were evaluated. Fenitrothion and esfenvalerate were applied so as to produce theoretical concentrations of 10 and 0.5 mg kg, respectively. Two hours after treatment, the grains were processed and deposition was analyzed by gas chromatography. Grain species did not influence insecticide stability. This stability was only dependent upon processing method and insecticide. Grains processed together with dry ice provided the greatest percentage of recovery for both insecticides. Regardless of processing method used, more esfenvalerate than fenitrothion was recovered, thus demonstrating the greater stability of the pyrethroid during this operation. The factors that influenced insecticide stability are discussed in the present work.