A rapid and simple method for the extraction and quantification of the herbicide atrazine, the atrazine hydroxylating agent in maize plants DIMBOA, and the hydroxylated product hydroxy-atrazine, is described. These substances were quantified by means of HPLC techniques, employing a RP-18 column and a mobile phase of methanol:water (40:60), buffered at pH 7,4. This method was developed to determine the efficiency of the atrazine hydroxylation detoxifying mechanism in maize plants cultivated under different environmental stress conditions.