A cyclic voltammogram of aclonifen was obtained on a glassy carbon electrode at pH 4.0 during the potential scan from 0.00 mV to 1400 mV vs. Ag/AgCl (3 mol L-1 NaCl). From repetitive cyclic voltammograms, one anodic peak at + 1175 mV and one cathodic peak on the reverse scan at + 350 mV were recorded. The sensitive square wave anodic peak at + 1220 mV was linearly related to aclonifen concentration ranging from 0.245 to 3.70 mu g mL(-1). The limit of detection (LOD) and the limit of quantification (LOQ) were 0.073 mu g mL(-1) and 0.245 mu g mL(-1), respectively. The percent recoveries of aclonifen calculated from soil and water samples spiked with 1.0 mu g mL(-1) level were 98.80% and 102.40% with the relative standard deviations of 1.82 and 3.61%, respectively. The method was also applied to the herbicide formulation Challenge (R) 600 and the average content of 595.3 +/- 9.73 g L-1 (n = 7, % 95 confidence interval) was consistent with the 600 g L-1 aclonifen level quoted by the manufacturer. The considerably high recoveries and low standard deviations provide evidence for the high accuracy and precision of the recommended method.