Data from the second National Health and Nutrition Examination Survey showed that 22 per cent of persons six months through 74 years old had blood lead levels under 10 μg per deciliter; 1.9 per cent had elevated levels (≥30 μg per deciliter [≥1.45 μmol per liter]). Among children six months through five years old the prevalence of elevated levels was significantly higher (4 per cent) than previously predicted on the basis of fewer data. The prevalence of elevated lead levels was 12.2 per cent in black children and 2.0 per cent in white children. Mean levels of blood lead were higher in blacks than whites among children and adults, among young children living in urban and rural areas, and among members of low-income, moderate-income, and higher-income families. These racial contrasts may reflect different lead exposure or absorption (or both). Young children from families (both white and black) whose incomes were under $6,000 had a significantly higher prevalence of elevated lead levels than those from households with incomes of $6,000 or more. (N Engl J Med. 1982;307:573–9.)