This paper addresses the use of genetic biomarkers in occupational epidemiology and some of the scientific, ethical, and social implications for epidemiologists and practitioners to consider, including issues involving individual risk estimation, the communication of epidemiologic results, and the translation of epidemiologic data into clinical or occupational health practice. Three scenarios from the occupational setting illustrate some of these issues and implications. The scenarios involve glutathione-S-transferase theta 1 (GSTT1) and hematopoietic cancer in hospital workers, human leukocyte antigen coding for glutamic acid in the 69th position (HLA DPB1(E69)) and chronic beryllium disease in beryllium workers, and peripheral myelin protein 22 (PMP22) deletion and carpal tunnel syndrome in railroad track workers. Epidemiologic research involving genetic biomarkers requires the application of genetic tests and can be considered on a continuum between basic sciences and clinical and occupational and public health practice for which questions of test relevance, validity, and utility become important.