Hexazinone is an example of an atypical triazine herbicide used for control of woody plants in reforestation areas and for selective weed control in sugarcane, pineapple, and alfalfa. The degradation of hexazinone in the rat, alfalfa, and sugarcane was originally reported by Holt (1981). The mass spectral identification of hexazinone metabolites isolated from rat urine and from sugarcane extracts was reported by Reiser et al., (1983). Established sugarcane plants grown in the greenhouse were treated by soil drench with 14C-hexazinone and harvested at plant maturity 6 months later. The total radioactive residues in mature sugarcane were less than 0.1 ppm, and the intact parent was not detected. Three major plant metabolites were identified by gas chromatography/mass spectroscopy (GC/MS) as their trimethylsilyl derivatives. They were metabolites A [3-(4-hydroxycyclohexyl)-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione], C [3-(4-hydroxycyclohexyl)-6-(methylamino)-1-methyl-,3,5-triazine-2,4(1H,3H)-trione], and E [3-(4-hydroxycyclohexyl)-1-methyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione]. The three major rat urine metabolites were A, B [(3-cyclohexyl-6-(methylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione)], and C. Minor metabolites in urine were D [3-cyclohexyl-1-methyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione] and F [3-cyclohexyl-6-amino-1-methyl-1,3,5-triazine(1H,3H)-dione]. The metabolic pathway for hexazinone in plants and animals is presented in Figure 7.11 and involves the processes of hydroxylation, demethylation, and deamination.