J-2931 (2,4-bis(1,1-dimethylethyl)-6-[(4-methoxyphenyl)methyl]1-methoxybenzene) had high activity against both organophosphorous-susceptible and -resistant strains of mosquitoes in both laboratory and field trials. No deleterious effects on nontarget organisms were observed. Bluegill sunfish, Lepomis macrochirus Rafinesque, accumulate up to ca. 70-fold the concentration of J-2931 in water in their tissues, but these residues decine rapidly when treated fish are placed in fresh water. J-2931 has a low water solubility (0.015 ppm) but is stable at a pH range from 6.5 to 10.0 at temperatures from 10 to 38°C; its persistence in water declines rapidly with increasing temperature in the presence of sunlight. Methods for the analysis of J-2931 in water, soil, grass, and fish tissues are presented.