The problems, characteristics, benefit programs, and medical aspects of work disability were reviewed. Total disability program expenditures increased to an estimated 114.2 billion dollars in 1975, or 7.9 percent of the gross national product (GNP). A 1972 survey showed that the prevalence of work disability was higher among older workers, decreased with increased education, was higher among blacks than among whites, and was 1.5 times more common in the South than in other parts of the country. Disability showed a strong relationship with occupation and industry. Men most likely to become disabled were farmers and farm managers, transport workers, salesmen, and service workers. Among men under age 35 almost 10 percent who worked in sales in 1972 reported some disability in 1974. The construction industry was the most hazardous for younger workers. Among disabling conditions, a chronic physical and mental disease or impairment was always a factor. The highest prevalence and severity in the 20 to 64 year population was in cardiovascular and musculoskeletal disorders. Disability benefit programs varied significantly. Social Security disability insurance has been the basic income maintenance program for the disabled in the United States. In addition, workers' compensation programs were in force in all states and insurance programs covered select groups of workers. The role of physicians is said to be critical in identification, assessment, and medical management of disease or injury. A major source of information on long term work disability was the surveys conducted by the Social Security Administration. Epidemiologic data were used for identification of work hazards and for determination of effects of disease or disability on an employee's work capability.