When epidemiology began to assert its place as a significant scientific discipline in the mid-20th century, there were few texts to assist students or their teachers. Indeed, the methods and rigors of the discipline were just beginning to be defined and refined. Consequently, most teachers had to develop their own class notes and exercises. Over the next 2–3 decades, a number of “introductory” texts appeared, aimed largely at the needs of undergraduate students and those such as clinicians with an “amateur” or “beginner's” interest in the subject. Other texts of interest to epidemiologists appeared that elaborated on the more technical aspects of certain related subjects, such as statistics and social sciences applied to medicine. There was little, however, to meet the needs of graduate students and their teachers and of career epidemiologists looking for a more detailed description of the increasingly sophisticated methodologies of their discipline. This book is designed to meet that need and, as such, will be widely welcomed.