Heterocyclic compounds hold a special place among the pharmaceutically significant natural products and synthetic compounds. Syntheses of various heterocycles have been research objective for over a century. The chemistry of heterocyclic compounds and their synthetic routes form the platform of medicinal, chemical and pharmaceutical research. The remarkable ability of heterocyclic nuclei to serve both as biomimetic and reactive pharmacophores made them key elements of numerous drugs. Heterocyclic compounds are an integral part of organic synthesis. Nearly more than half of the known organic compounds contain at least one heterocyclic ring. Many heterocyclic compounds occur naturally and are actively involved in biological processes, like nucleic acid bases, which are derivatives of the pyrimidine and purine rings systems, as being crucial to the mechanism of replication. Hence the present work entitled "SYNTHESIS OF THIAZOLIDINONES AND IMIDAZOLES" was undertaken and the details of the synthetic work, microbial screening and characterizations of the intermediates and desired products have been discussed in this book.