Impairment evaluation of the spine has evolved notably since the 1958 publication by the American Medical Association of an article titled A Guide to the Evaluation of Permanent Impairment of the Extremities and Back. Significant differences exist among the editions of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) currently in use, including the third edition, revised (1988), fourth (1993), fifth (2000), and sixth (2008) editions. This article reviews exemplary cases according to the instructions and methods of each edition, beginning with a table that summarizes spinal impairment criteria by edition of the AMA Guides. Another extensive table presents seven exemplar cases that demonstrate the differences in impairment ratings between the fourth, fifth, and sixth editions; each example is discussed in terms of different approaches taken in each of these editions. In the AMA Guides, Sixth Edition, the process of rating impairment was simplified by the elimination of the range of motion method. In the examples presented, the impairment values calculated using the sixth edition fall between those obtained using the fourth and fifth editions. Evaluating physicians must know the appropriate edition of the AMA Guides to use in each case and must understand the differences between them, particularly the changes included in the sixth edition.