Investigations showing the effective use of simazine [2-chloro-4,6-bis (ethylamino)-s-triazine] as a selective herbicide in several crops particularly in corn has resulted in a demand for information about its degradation in plants. It is extremely important then to know if toxic residues remain in plants. Evidence to the contrary would be obtained if plants treated with simazine uniformly labeled with carbon-14 in the triazine ring were found to respire radioactive carbon dioxide.