The role of epidemiologic surveillance in occupational health was discussed. The nature and purpose of surveillance programs as applied in occupational health programs were summarized. Occupational surveillance programs are intended to identify cases of illness, injury, or excessive exposure and monitor trends in their occurrence as a function of industry, time, or geographic area. Identifying cases of occupational injury, illness, or excessive exposure can benefit not only the affected worker as well as his coworkers. Trend monitoring is regarded as an essential component in the evaluation of the overall effectiveness of worksite control programs. Procedures for obtaining data and identifying cases in health surveillance programs were summarized. Techniques for trend monitoring were described. Methods for monitoring occupational exposures were discussed. The surveillance activities of OSHA, the Mine Safety and Health Administration, and NIOSH were mentioned. Evaluating the usefulness of surveillance programs was discussed. Recent trends in surveillance programs were reviewed. These included strengthening morbidity surveillance systems, standardizing questionnaires and diagnostic tests used in surveillance programs, improving employer reporting, improving the ability of state health departments to perform occupational health surveillance, improving national surveys, and improving exposure surveillance. The authors conclude that surveillance in occupational health is a complex process and no single approach is able to address all of the needs of occupational health and safety.