A new gas-liquid chromatographic (GLC) procedure has been developed for the analysis of diflubenzuron, 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl) urea, in pond water. The residues from fortified pond water were extracted with ethyl acetate, derivatized, and cleaned up on a mini Florisil column. The diflubenzuron was determined by GLC as its N,N′-di(trifluoroacetyl) derivative, using electron capture detection. A 50% full scale deflection was obtained with 0.03 ng injected. Recoveries from fortified unfiltered pond water were 65.7, 72.8, 82.0, and 90.8% at the 0.020, 0.059, 0.197, and 0.788 mg/L (ppm) levels, respectively. Recoveries from fortified filtered pond water were 94.1 and 89.3% at the 0.020 and 0.060 mg/L levels, respectively. It is postulated that diflubenzuron is immobilized by adsorption, for example, to particulate organic matter in the pond water because recovery data from unfiltered water followed the linear form of the Freundlich equation.