Abstract: A biochemical system in the determination of pesticides which is able to detect and measure the presence of parts per billion levels of different pesticides particularly in foodstuffs. The method employs insect tissues that contain specific binders or enzymes sensitive to various groups of pesticides. The sample or sample extract containing pesticides, radiolabeled pesticides and/or radiolabeled pesticide analogs and/or radiolabeled substrates is exposed to insect tissues containing receptors or enzymes. The pesticide competes with the radioactive tracers for the binders or the enzymes in the insect tissues. Residual enzyme activity or bound pesticides are measured. The extent of binding or enzyme activity may be inversely proportional, under standardized conditions, to the amount of pesticide in the sample.