THE FOURTH EDITION OF MODERN EPIDEMIOLOGY ARRIVES 35 YEARS AFTER THE FIRST EDITION, WHICH WAS A MUCH SMALLER SINGLE-AUTHORED VOLUME THAT OUTLINED THE CONCEPTS AND METHODS OF A RAPIDLY GROWING DISCIPLINE. THE SECOND EDITION, PUBLISHED 12 YEARS LATER, WAS A MAJOR TRANSITION, AS THE BOOK GREW ALONG WITH THE FIELD. IT SAW THE ADDITION OF A SECOND AUTHOR AND AN EXPANSION OF TOPICS CONTRIBUTED BY INVITED EXPERTS IN A RANGE OF SUBDISCIPLINES.