Epidemiology is the study of frequency, distribution and determinants of health related phenomenon. This book is a simple way of presenting the subject. It present the subject in a sequence in which usually undergraduates are introduced to the subjects. The presentation of ideas, examples and exercises are given in reader-friendly fashion. The whole subject has been divided into five modules. Each module has been divided into small chapters comprising of learning material for one hour’s class. Each chapter has been planned based on objectives to be achieved by learning them. The content of each chapter has been organized to the tune of questions asked in undergraduate examinations with utmost conscious effort to preserve the depth of the subject handled. Difficult and related concepts are repeatedly explained in appropriate situations. Each chapter has exercises. Examples may be hypothetical or real. Real ones are drawn from classical studies as well as local experiences appropriate to the topic. Worked out examples in each chapter are expected to illustrate the principle involved in making statistical inferences. The content of this book has been drawn heavily from many other standard textbooks, but presented in a different style and order with the author concepts and ideas integrating them. The emphasis is for the subject epidemiology. All other subjects are treated as tools that are used by epidemiologists. Topics are discussed as in a classroom setting with specific learning objectives set for each chapter. Textbooks that have been referred for writing the specific chapters are listed at the end of each chapter for further reading.