Amitrole is a nonselective polar herbicide that can easily pollute ground and surface waters because of its high solubility in water. A precolumn derivatization high-performance liquid chromatographic method for amitrole analysis has been developed. Derivatization of amitrole was performed with 4-chloro-3,5-dinitrobenzotrifluoride (CNBF). The derivatization conditions and the influence of elution composition on the separation were investigated. In pH 9.5 H(3)BO(3)-Na(2)B(4)O(7) media, the reaction of amitrole with CNBF was complete at 60 degrees C after 30 min. The stability of the derivative under light irradiation and room temperature in methanol-water samples was demonstrated. The derivatized amitrole was separated on a K C(18) column (250 mm x 4.6 mm, 5 microm) at room temperature, and UV detection was applied at 360 nm. The separation of derivatized amitrole was achieved within 18 min by gradient elution mode. The method correlation coefficient was 0.9995, in concentrations ranging from 1.59 to 318 mg L(-1). The detection limit of amitrole was 0.16 mg L(-1) with a signal-to-noise ratio of 3. The proposed method was applied to the quantitative determination of amitrole in environmental water with recoveries of 92.0-103.0% and RSDs of 2.22-6.26, depending on the sample investigated. This method has good accuracy and repeatability that can be used to quantify amitrole in environmental water.