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. This edition includes numerous improvements and several new chapters which will further enhance its appeal.