Although several states use the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) when they evaluate individuals with impairments and disabilities, various disability systems exist in the United States. Disability and compensation systems have arisen to ensure that disadvantaged members of society with a medically determinable impairment, which may lead to a disability, have recourse to compensation from various sources, including state and federal workers’ compensation laws, veterans’ benefits, social welfare programs, and legal avenues. Each of these has differing definitions of disability, entitlement, benefits, procedures of claims application, adjudication, and the roles and relative weights assigned to medical vs administrative deliberations. Workers’ compensation statutes were enacted because of inadequacies of recovery from claims for injured workers under common law. Workers’ compensation is a no-fault system adopted to resolve the dilemmas of tort claims by providing automatic coverage to employees injured during the course of employment; in exchange for coverage, employees forego the right to sue the employer except for wanton neglect. Other workers’ compensation programs in the United States include the Federal Employees Compensation Act; the Federal Employers Liability Act (railroads); the Jones Act (Merchant Marine Act); the Longshore and Harbor Workers’ Compensation Act; the Department of Veterans Affairs; Social Security; and private, long-term disability insurance.