The chemical structure of the compounds found by the reaction of cyanogen bromide and acylhydrazines was determined as 2-alkyl-5-amino-1, 3, 4-oxadiazoles (I). 3-Alkyl-5, 6, 7, 8-tetrahydro-s-triazolo [4, 3-b] [1, 2, 4] triazine-6, 7-diones (III), which are listed in Table III, were prepared from 4, 5-diamino-1, 2, 4-triazoles (II) and diethyl oxalate. Several unreported intermediates of these compounds - 2-alkyl-5-amino-1, 3, 4-oxadiazoles (I) and 4, 5-diamino-1, 2, 4-triazoles (II)-were also prepared and are listed in Tables I and II.