Advancement of medicinal chemistry in this century has been possible due to the integration of various disciplines like organic chemistry, pharmacology, molecular biology, biochemistry and other allied subjects that work hand in hand as a team.A successful medical agent has its birth in stages viz. chemical synthesis, screening for activity/activities, toxicological studies, metabolic studies, clinical trials of a tolerance tests, teratogenic tests, QSAR studies and so on. The biological action of a drug occurs due to the interaction of molecule with other specific molecules or receptors or enzymes. Ariens later elaborated the concept of receptor theory.The isosteric replacement of -O-, -S- and -N- gives rise to the compounds, benzoxazole, benzothiazole and benzimidazole respectively