CLINICAL EPIDEMIOLOGY HAS EXTENDED TO KNOWLEDGE TRANSLATION AND PATIENT ENGAGEMENT TOGETHER WITH ENDEAVORS TO IMPROVE HEALTH-RELATED BEHAVIORS USING IMPLEMENTATION SCIENCE, AND AVAILING OF ADMINISTRATIVE DATABASES AND BIG DATA TECHNOLOGY. ISSUES RELATED TO RESEARCH DESIGN, MEASUREMENT, AND EVALUATION ARE CRITICAL TO CLINICAL EPIDEMIOLOGY. THIS THIRD EDITION OF CLINICAL EPIDEMIOLOGY: PRACTICE AND METHODS HAS UPDATED CHAPTERS ON LONGITUDINAL STUDIES, RANDOMIZED TRIALS, OTHER RESEARCH METHODS, AND EVIDENCE-BASED DECISION-MAKING, AND INCLUDES A NEW SECTION ON CHANGING HEALTH-RELATED BEHAVIORS. ITS INTENDED REACH IS CONSEQUENTLY WIDE NOT ONLY TO INCLUDE TRAINEES IN CLINICAL EPIDEMIOLOGY AND RESEARCHERS WHO WANT TO UNDERTAKE CLINICAL RESEARCH, WHETHER THEY BE CLINICAL PRACTITIONERS OR BASIC SCIENTISTS WHO WANT TO EXTEND THEIR WORK TO HUMANS, BUT ALSO USERS OF CLINICAL RESEARCH FINDINGS WHETHER THEY BE CLINICAL PRACTITIONERS OR DECISION MAKERS IN THE HEALTH SYSTEM.