Some novel chromeno[2,3-d]pyrimidinone, pyrano[2,3-d]pyrimidine, dihydropyrimidine, pyridopyranopyrimidine and pyrimidopyranopyrimidine have been synthesized. The structures of target compounds were confirmed by elemental analyses and spectral data. The antimicrobial activity of all the target synthesized compounds were tested against various microorganismst such as Pseudomonas aeruginosa; Staphylococcus aureus (Bacteria), Aspergillus flavus (Fungus) and Candida albicans (Yeast fungus) by the disc diffusion method. In general, the novel synthesized compounds showed a good antimicrobial activity against the previously mentioned microorganisms.