interaction of amidrazones and isocyanate esters in dimethylformamide produces good yields of 4-substituted -1-imidoylsemicarbazides. They are unaffected by acids, but are cyclised to 3-alkyl (or aryl)-1,2,4-triazol-3-ones or their 4-substituted analogues in alkaline media. Analogous linear adducts arising in good yields from amidrazones and ethoxycarbonyl isothiocyanates are cyclised to 3-substituted