We have found that refluxing an aqueous suspension of compound 1a in the presence of hydrochloric acid and steam distillation of the aldehyde evolved gave 5-oxo-1, 2, 4-triazole-3- carboxylic acid 2a in 70% yield. Acid 2a was also prepared by us from 6-amino-2, 3, 4, 5- tetrahydro-1, 2, 4-triazine-3, 5-dione (4) by the method reported in the literature [1].