An easy and selective spectrophotometric method was developed for the determination of metamitron in presence of organic matter and iron, which interferences were eliminated by Partial Least Sq uares Regression Type I. The calibrat ion model was constructed fro m a series of 21 samp les, which concentrations varied in the range from 0 to 15 g mL -1 of metamitron, fro m 0 to 400 g mL -1 of humic acid sodium salts and from 0 to 50 g mL -1 of ferric sulfate. For a series of 15 validation samples, a 95 ± 6 % of mean percentage recovery and a standard error of pred iction of 0.55 were obtained, through a calibrat ion model constructed with two factors fro m 251 to 350 n m as wavelength interval, mean centering data. Finally, a mean recovery percentage of 90 ± 11 % was obtained in the analysis of aqueous leachates fortified with metamitron, obtained fro m a sandy loam soil with an organic content of 2.5 %.