The synthesis and structural properties of two kinds of thiosemicarbazide derivatives (2a-c and 3a-c) and one kind of semicarbazide derivatives (4a, 4b) have been described. These compounds were synthesized by treating 2-(4-amino-3-alkyl-5-oxo-4,5-dihydro-lH-1,2,4-triazol-1-yl)acetohydrazides (la-c) with benzyl isothiocyanate, 3-florophenyl isothiocyanate and benzylisocyanate, respectively. The synthesis of 4amino-3-alkyl-l-[(4-alkyl-5-mercapto(or 5-oxo)-4H-1,2,4-triazol-3-yl)methyl]-4,5-dihydro-lH-1,2,4-triazol-5-ones (5a-c, 6a-c and 7) have been performed from the reaction with sodium hydroxide. On the other hand, the acidic treatment of compounds 2b, 3b and 4b has afforded 4-amino-3-(4-chlorobenzyl)-1-[(5alkylamino-1,3,4-thidazol(or 1,3,4-oxazol)-2-yl)methyl]-4,5-dihydro-lH-1,2,4-triazol-5-ones (8, 9 and 10). The condensation of thiosemi(or semi)carbazide derivatives (2a-c, 3c and 4b) with 4-chlorophenacyl-bromide have resulted in the formation of 2-[4-amino-3-alkyl-5-oxo-4,5-dihydro-lH-1,2,4-triazol-1-yl]-N'(3,4-dialkyl-l,3-thiazol(or oxazol)-2(3H)-yliden]acetohydrazides (lla-c, 12, 13), while their condensation with chloroacetic acid has produced 2-[4-amino-3-alkyl-5-oxo-4,5-dihydro-lH-1,2,4-triazol-1-yl]-N'-[3-(3alkyl)]-4-oxo-1,3-thiazolidin(or oxazolidin)-2-yliden}acetohydrazides (14, 15 and 16). The spectral data and elemental analyses have support the proposed structures.