This book represents an introduction to medicinal chemistry and the therapeutic applications of various triazole, coumarin and pyridine derivatives. The chemistry of mentioned heterocycles has also been discussed. We have synthesized some new triazole-coumarin-pyridine hybrids via thioether linkage and evaluated for their in vitro antibacterial and antifungal activity. All the newly synthesized derivatives were well characterized by their IR, 1H NMR and mass spectra.