Papers on biological monitoring and medical screening of workers for the effects of occupational exposure were presented at a conference in Cinncinnati, Ohio, in July 1984. Articles on these techniques as practiced in industry were included. Legal, ethical, and social consequences were covered. The need for adequate evaluation of effectiveness was emphasized. Many new methods, especially in the areas of biological monitoring for the presence of intoxicants or their metabolites and medical screening for early evidence of genetic and somatic damage are being developed. The place of these two techniques in the continuum of methods available for the prevention of occupational disease was considered. Along with the biological aspects of screening tests, aspects of public health policy and economics are dealt with, as well as numerous case studies presenting the actual experience of screening programs. Complexities, such as elucidating the relationship between multiple causes, the host, and the effect, were addressed. The papers deal with urinalysis, blood analysis, breath analysis, immunoassay, radiodiagnosis, pulmonary function screening, sputum cytology, fecal hemoccult testing, birth weight, and sigmoidoscopy.