Widely accepted as the most reliable medical reference on impairment evaluation since its inception in 1971, the Guides is highly valued by physicians who use its authoritative chapters to determine how to assess for impairment. The new edition of the Guides continues to build from this legacy by focusing on physician interrater reliability through an updated consensus approach that considers the latest evidence and patient function. The result is a new standard that seeks to evaluate impairment using a series of uniform grids for each chapter. Covering every body system, Guides Sixth Edition provides a standardized approach to determine impairment assessment using patient history, physical examination and clinical tests. Uniformity and ease of use is stressed to provide a consistent rating for conditions in each of the body systems using evidence based methodologies and, when lacking, a consensus approach. The Guides was developed with open deliberations from participating national medical specialty societies and state medical associations. An oversight advisory panel was established to broaden fuller participation of stakeholders. An Editorial Panel was created to review past editions and make recommendations and oversee the development of the Sixth Edition. An expansive stakeholder review was implemented to ensure consensus based content and expert medical review.