The toxic effects of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) to barley were avoided by feeding plants treated with 1.5 lb/A of simazine, sucrose, glucose, aspartate, and maltose. Shoots from plants fed glucose and maltose contained more soluble carbohydrate than the check. Plants fed glutamine and asparagine were higher in total nitrogen content than the check. Plants fed sucrose and maltose increased their nitrogen content over the check, but plants fed glucose did not. The harmful effects of simazine occurred primarily in barley shoots exposed to light. Plants grown in the dark showed a very small decrease in weight of shoots and soluble carbohydrate content as the level of simazine increased, while the weight of the shoots and soluble carbohydrate content of treated plants grown in the light decreased sharply. Simazine had little effect on root growth of plants grown in the light or dark. The data on root respiration showed that barley roots metabolized the added substances differently and that simazine differentially influenced their metabolism by the roots.