"Work-related diseases" are multifactorial diseases in which the work environment plays a partial role in causation. They include chronic noncommunicable disease affecting working populations. There is evidence that such diseases as musculoskeletal disorders, hypertension, chronic bronchitis, and several psychosomatic disturbances affecting workers can be attributed to a variety of risk factors, including those in the workplace. Examples of investigations and the occurrence of various work-related diseases are cited from several countries. Occupational health is evolving to deal with multifactorial health problems from combined exposure to occupational and other environmental factors, life-style, and individual susceptibility. More attention should be given to psychosocial factors and ergonomics in the workplace, workers' participation and life-style, multifactorial occupational epidemiology, and new approaches to legislation. A list of research areas is given to cover the present gaps in knowledge. The World Health Organization has started a program of work in this field to identify the magnitude of these diseases in various parts of the world, to stimulate epidemiologic research, and to develop guidelines for control measures.