s-Tetrazines having aryl substituents in either the 3- or 3,6-positions react readily with alkyl or aryl Grignard reagents to give 1-alkyl (or aryl)-1,4-dihydro-s-tetrazines. The 1-alkyl-1,4-dihydro-s-tetrazines rearrange in methanolic hydrogen chloride to 4-alkylamino-1,2,4-triazoles, but thermolyse readily to the less well known, isomeric 1-alkylamino-1,2,4-triazoles. Possible reaction pathways involving breakdown to nitrile and reactive intermediates such as 1,3-dipolar species are discussed.