The diagnosis of occupational illnesses may be considerably more difficult than is the case with occupational injuries because of a variety of factors: an intervening latency period, uncertainty in identifying the most significant chemical or physical exposures, determination of exposure levels retrospectively, and coordination of the physician with regulatory and workers' compensation bureaucracies. Such problem-solving techniques as retrospective industrial hygiene and attention to in-situ chemistry can act as means of reducing the uncertainty in making the diagnosis of occupational illness. Advance familiarity with workers' compensation and state or federal regulatory agencies can further facilitate diagnosis and patient advocacy.