Many states require the use of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) in their workers’ compensation systems. In 20 states (see Table), this requirement is specified by statute (a law that is enacted and passed by a state's legislature). The state statutes that deal with the AMA Guides may or may not specify which edition to use and how to use it. In any case, ultimately it is the responsibility of the courts to interpret these statutes, which may be ague, to determine which edition of the AMA Guides should be used and to establish how that edition should be used. Evaluators should use the edition of the AMA Guides that is required by the local regulatory authority because of an incorrect version of the AMA Guides could result in judicial invalidation of an impairment rating (see, eg, McCabe v North Dakota Workers’ Compensation Bureau). A table that identifies the edition used and authorizing statute number for the 20 states is included.