Epidemiology is the basic tool of Public Health. It is the most important tool that forms the basis of any research. This book tries to summarize the history, aims, uses, various basic measurements in epidemiology. The methods and concepts explained in various textbooks and other sources have been put together in this book. This will facilitate the reader to find them all in one book. This book provides all the important concepts and methods in a form that is easily understandable to the reader.