The chronic respiratory diseases are a pervasive cause of morbidity and mortality. In the developed countries the chronic nonspecific respiratory diseases (CNRD), eg, chronic bronchitis, emphysema, bronchial asthma, are a major cause of morbidity and mortality. They have been increasing during a period when, in many countries, there has been a decline in total mortality rates and in certain major chronic illnesses such as coronary heart disease. In many developing countries, acute and chronic respiratory diseases are leading causes of death with chronic bronchitis as a major cause of disability. The boundary between occupationally caused and "work-related" chronic lung diseases is indistinct, reflecting the multifactorial nature of the diseases. This report focuses primarily on the CNRD, and the work-related risk factors which play a role in their etiology and/or aggravation. These factors include specific work exposures such as inhaled noxious materials and other work conditions, immunologic considerations, combined exposures in the work and community environment, societal trends such as industrialization and urbanization, behavioral patterns, stress, social support, and other socioeconomic elements. The available evidence is examined, and directions are indicated for further research for the identification of those factors in the environment which initiate, potentiate, or aggravate CNRD and for the development of measures for the prevention of disability and premature death.