A square wave cathodic stripping voltammetric (SWCSV) method has been developed for the determination of insecticide diafenthiuron. The procedure is based on controlled accumulation of the insecticide on a static hanging mercury drop electrode (SHMDE) at 0.00mV (vs. Ag/AgCl) in Britton-Robinson buffer solution (pH 7.0). The insoluble mercury compound was reduced at -510mV during the cathodic potential scan. The peak currents were linearly related to insecticide concentration between 30.4 and 3200 mu g L(-1). The detection and quantification limit were 9.1 mu g L(-1) and 30.4 mu g L(-1), respectively. The proposed analytical procedure was applied to natural water and soil samples. The method was extended to direct determination of diafenthiuron in insecticide formulation Polo (R) 50 WP and average content of 50.3 +/- 1.7 (m/m) at 90% confidence level, in close agreement with the 50.0% quoted by the manufacturer. HPLC comparison method indicated that accuracy was in agreement with that obtained by the proposed method.