Medical surveillance of workers exposed to potential respiratory hazards may be a valuable tool in early recognition and prevention of certain occupational lung diseases. The use of pulmonary function tests, particularly spirometry, has been widely accepted as an integral part of respiratory surveillance. A National Aeronautics and Space Administration contract report on the Occupational Safety and Health Administration medical and workplace surveillance requirements and recommendations by the National Institute for Occupational Safety and Health is a recent detailed study of medical surveillance requirements and recommendations (unpublished study, 1983). This paper is a brief guide for those in the medical profession attempting to establish or improve their medical surveillance programs for occupational respiratory diseases. It describes procedures to use and techniques for interpreting test results, and finally includes a study of normal reference values. In addition, the references should provide additional information for establishing a respiratory medical surveillance program.