The major pathway of atrazine metabolism in intact sorghum was shown to involve the following steps: atrazine 'right arrow' S-(4-ethylamino-6-isopropylamino-1,3,5-triazin-2-yl)glutathione 'right arrow' gamma -glutamyl-S-(4-ethylamino-6-isopropylamino-1,3,5-triazin-2-yl)cysteine 'right arrow' S-(4-ethylamino-6-isopropylamino-1,3,5-triazin-2-yl cysteine 'right arrow' N-(4-ethylamino-6-isopropylamino-1,3,5-triazin-2-yl)cysteine 'right arrow' N-(4-ethylamino-6-isopropylamino-1,3,5-triazin-2-yl)lanthionine. From 40 to 87% of the atrazine entering sorghum through the roots was estimated to be metabolized via this pathway. Evidence indicated that atrazine can also be metabolized via this route after first undergoing N-dealkylation. The step involving conversion from the S- to the N-cysteine conjugate was shown to be a non-enzymatic rearrangement. This is the first reported occurrence of S-(4-ethylamino-6-isopropylamino-1,3,5-triazin-2-yl)cysteine, the lanthionine conjugate, 2-hydroxy-4-amino-6-isopropylamino-1,3,5-triazine and 2-hydroxy-4,6-diamino-1,3,5-triazine (ammeline) in sorghum. Structural formulae for these compounds and the metabolic pathway are shown. From summary