We examined the effects of methanol and temperature on the reactivity of monoclonal antibodies specific to the insecticide etofenprox. When the antigen-antibody reaction was done at 4 degrees C in 10% methanol, the sensitivity in the enzyme immunoassay with each antibody was more than 10-fold higher than that measured at 37 degrees C. Although in 10% methanol one of the antibodies reacted equally with both etofenprox and the carbonate-derivative of etofenprox, in 50% methanol the antibody reacted with etofenprox, but not with the derivative.