Pain and inflammation are simultaneous responses in bacterial infections. In current clinical practice, two groups of agents like antibacterial and non-steroidal anti-inflammatory drugs (NSAIDs) are prescribed simultaneously. Regrettably, none of the drug possesses these activities in a single component. Exploiting the bioisosterism concept, we have documented that 2-phenyl-3-substituted quinazolines, 2,3-disubstituted quinazolines, 2-methyl-3-substituted quinazolin- 4-(3H)-ones and 2-methylthio-3-substituted quinazolin-4-(3H)-ones exhibited good analgesic and anti-inflammatory activities. The present work is an extension of our ongoing efforts towards the development and identification of lead molecules by bioisostere concept, for which we designed some of 2-methylthio-3-substituted-5,6-dimethylthieno[2,3-d] pyrimidin-4(3H)-ones. The title compounds were investigated for analgesic, anti-inflammatory and antibacterial activities. While the test compounds exhibited significant activity, the compounds (6-9) showed more potent analgesic activity, and the compounds (8, 9) showed anti-inflammatory activity comparable to the reference standard diclofenac.