Following on in the footsteps of its acclaimed and popular predecessor, this new edition builds on the successful features that engaged readers of the first edition: it explains the principles and practice of epidemiology and serves as a handbook for those who wish to do epidemiology; it uses relevant exercises and examples, taken from real life, to illustrate how to set up a study; it aims to help produce valid results that will satisfy grant bodies, ethical committees and journal editors; ultimately it bridges the gap between theory and practice. By making the subject so easily accessible, it will be an excellent introduction for anyone who is training in epidemiology and public health, and for all those involved in medical research. This edition includes numerous improvements and several new chapters which will further enhance its appeal.