The continued occurrence of occupational lead overexposure and lead poisoning in the United States remains a serious problem despite awareness of its adverse health effects. Lead exposure is arguably the oldest known occupational health hazard. It is a particularly insidious hazard with the potential for causing irreversible health effects, including hypotension, central nervous system problems, anemia and diminished hearing acuity before it is clinically recognized. Scientific evidence of subclinical lead toxicity continues to accumulate, making further reduction in workplace exposure, regular screening, and earlier diagnosis and treatment of critical importance in the prevention of this occupational hazard. For the most part, the diagnosis of lead poisoning in the adult worker is based on the integration of data obtained from the history, a physical examination, laboratory tests and tests of specific organ function. A blood level of 40 micrograms per dL (1.95 mumol per L) or greater requires medical intervention; a level of 60 micrograms per dL (2.90 mumol per L) or three consecutive measurements averaging 50 micrograms per dL (2.40 mumol per L) or higher indicate the necessity for employee removal. The decision to initiate chelation therapy is not based on specific blood levels but depends on the severity of clinical symptoms.