2,3,5-trisubstituted-1,2,4-triazine-6-ones (2a,b) were synthesized by the cyclocondensation of oxazolinonederivatives (1) with semicarbazide and thiosemicarbazide. Acylation and condensation of triazine-6- one derivatives (2a,b) with acetic anhydride and 3-methoxy-2-hydroxybenzal dehyde yielded the corresponding N- acetyl derivatives (3a,b) and N-(3-methoxy-2-hydroxybenzylidene)amino derivat ives (4a,b). The structure of these synthesized compounds wascharacterized by 1 H-NMR, 13 C-NMR, Mass, IR and elemental analysis. All the synthesized 1,2,4-triazine-6-ones were tested for t heir cytotoxicity against HepG-2 cell line. Some of these compounds showed higher cytotoxicity activity than vinblastine standard