Abstract: On the basis of bio-isosteric principle, 10 compounds of the 2,4-diamino-5-(substituted anilino) pyrimidines were synthesized by condensation of 5-bromouracil with corresponding substituted anilines, followed by chlorination with POCl₃ and amination under high pressure. The antibacterial activities of these compounds on E. coli 1515 were also reported. Compounds 111₆(x=3-OC₄H₉-n) and 111₇ (x=2,4-(CH₃)₂) showed a fair antibacterial activity. Their activities probably depend on the hydrophobicity of pyrimidine compounds. Further studies are in progress.