A natural product in corn, the 2-glucoside of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one, is capable of inactivating triazine herbicides. Two essentially isogenic corn lines, Mississippi selection GT112 (susceptible to atrazine and simazine) and GT112 RfRf (resistant), contained the compound in both roots and shoots. The content of the roots was about equal for the two lines and decreased with age. In shoots of GT112 seedlings 13 to 28 days old, the 2-glucoside content reduced with time to half the original value. In shoots of GT112 RfRf, the 2-glucoside content doubled from 13 to 17 days, then decreased. Shoots of GT112 RfRf contained 1.6, 3.6, and 2.4 times more 2-glucoside at 13, 17, and 28 days, respectively, than GT112. However, 13-day-old homogenized shoots of GT112 converted 1.8 times more atrazine per μM of 2-glucoside than GT112 RfRf. Susceptibility of GT112 to triazine herbicides is not due to absence of the 2-glucoside or its inability to convert atrazine.