One of the most important areas of research in organic chemistry is heterocyclic chemistry. Heterocyclic compounds form a major class of organic compounds. Heterocyclic compounds have one or more hetero atoms in their structure. The simplest of five membered heterocyclic compounds are pyrrole, furan, thiazole, thiadiazole, and imidazole. Heterocyclic compounds are widely distributed in nature and are essential in our daily life processes. It has extensive range of applications in medicinal chemistry. Presently lots of heterocyclic compounds are known and day by day the number is increasing rapidly due to enormous synthetic research and their synthetic utility. They also have a vast number of applications in the field of agriculture, biochemistry, and electronics and as dyestuff. Some naturally occurring antibiotics like penicillin, cephalosporins have heterocyclic portion. The review article covers the most active heterocycles that have shown considerable biological actions as antifungal, antimalarial, anti-inflammatory, antineoplastic, anthelmintic, antiviral, anticonvulsant, diuretic activity, antiulcer, antidepressant and antibacterial activity and their sundry applications in electronics as organic conductors, biology, optics, pharmacology, as a dye, as a lubricating agent, as a corrosive agent, waterproofing agent etc.