1, 2, 3-oxadiazolium-5-olate (Sydnone) is used as a versatile synthon in heterocyclic synthesis. A large number of sydnone derivatives have been synthesized with biological interest and reported to possess a wide spectrum of biological and pharmacological activities like antimicrobial, anti-inflammatory, analgesic, anti-pyretic, antitumour, antiarthritic and antioxidant properties. Among all the mesoionic compounds, sydnone ring is the most widely studied because of ease of its synthesis from primary amines and it is the only mesoionic ring which undergoes a wide variety of chemical reactions of synthetic utility. Sydnones form a subclass of mesoionic compounds which again form a subclass of mesomeric betaines. These characteristics of five membered heterocyclic mesoionic compounds have encouraged concentration on the study of chemical, physical and biological properties of sydnones, as well as their potential applications. Thus there is wide scope to explore more novel sydnones as a potent biodynamic molecules.