Data from 4,500 workplaces surveyed by the National Institute for Occupational Safety and Health (NIOSH) in the National Occupational Hazard Survey (1972 to 1974) and National Occupational Exposure Survey (1981 to 1983) show an increase in both preplacement and periodic medical screening in US industries during the past decade. The distribution of screening is primarily related to plant size, but also varies considerably by industry type; further, plants with industrial hygiene and safety programs and/or unions are more likely to provide screening examinations than those without, irrespective of plant size. As for workers potentially exposed to selected chemical hazards, the first survey provides no consistent evidence that such workers were more likely to receive exposure-specific tests than other workers. The significance of these findings is discussed in the context of the proposed framework for medical screening practices developed by NIOSH researchers.