In December 2007, the American Medical Association published the sixth edition of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), following previous editions published in 2000 (fifth edition) and 1993 (fourth edition). To assess the effects of changes in whole person impairment ratings across editions, the authors selected 200 cases of whole person impairment and reevaluated each according to criteria in the three editions. Interrater reliability was confirmed when an independent reviewer checked 15% of the cases and found agreement within 1% in all but one of the thirty cases checked. Tables and figures in the article compare average whole person impairment in terms of sixth edition chapters; by edition; and by category (nonsurgical vs surgical intervention) and edition. On the basis of the sample and their comparisons, the authors conclude that the effect for patients based on their diagnostic impairment is small, and greater difference is seen for results obtained using the fifth edition compared with the fourth edition. The observed changes were expected and result primarily from the following: surgery and therapy should improve function and thus should not routinely increase impairment; there are improved functional outcomes for carpal tunnel syndrome and total joint replacement; and certain common conditions that resulted in functional deficits but no ratable impairment in previous editions now should be ratable. The study showed excellent interrater reliability with sixth edition ratings, which was an important goal for the new edition.