Welcome to the drug discovery and development course. My aimis to attract the interest of the undergraduate students, so that they feel a spontaneous urge to explore and understand the basic concepts of drug discovery and development. These students often encounter enormous difficulties in grasping the fundamentals of synthesis of simple as well as complex compounds including those belonging to the therapeutic group, and they often get confused when they are supplied with inadequate information of vitally important medicinal compounds, their chemical formulae andchemical names and their mechanism of action. So my aims at removing this inadequacy by furnishing copious information about medicinal compounds and pointing out their inter-relations wherever they exist. Thus, in this study guide an attempt has been made to include and correlate detailed accounts of most of the important categories of drugs for this course.