A main objective of the present research study is to synthesize series of novel fused 8-substituted 3,4-dihydro-6-methyl-4-(2,4-dinitrophenyl)imidazo[1,5-b][1,2,4]triazin-2(8H)-one derivatives and to evaluate them for their anti-inflammatory and ulcerogenic effect. The stated compounds were synthesized with the initial reaction of various aromatic aldehydes and N-acetylglycine in acetic anhydride and anhydrous sodium acetate by Erlenmeyer-Azlactone synthesis to give oxazol-5(4H)-one derivatives which on reaction with substituted phenylhydrazine in dry benzene gave 1H-imidazol-5(4H)-one derivatives and lastly condensation with chloroacetamide in N,N-dimethylformamide gave stated compounds. All synthesized compounds were characterized by FT-IR, 1H NMR, 13C NMR, LC-MS and HPTLC etc and are well supported by spectroscopic data. The anti-inflammatory and ulcerogenic activities were compared with standard drug indomethacin and synthesized compounds were found to be less ulcerogenic as compared with standard drug. Compounds belonging to series 7 are more active than series 5 and former are less ulcerogenic than standard drug.