Lead is an environmental toxicant that may deleteriously affect the nervous, hematopoietic, endocrine, renal, and reproductive systems. Lead exposure in young children is a particular hazard because children absorb lead more readily than do adults and because the developing nervous systems of children are more susceptible to the effects of lead. Blood lead levels (BLLs) at least as low as 10 micrograms/dL can adversely affect the behavior and development of children. CDC's National Health and Nutrition Examination surveys (NHANES), an ongoing series of national examinations of the health and nutritional status of the civilian noninstitutionalized population, have been the primary source for monitoring BLLs in the U.S. population. From NHANES II (conducted during 1976-1980) to Phase 1 of NHANES III (conducted during October 1988-September 1991), the geometric mean (GM) BLL for persons aged 1-74 years declined from 12.8 micrograms/dL, and the prevalence of elevated BLLs (BLLs > or = 10 micrograms/dL) decreased from 77.8% to 4.4%. This report updates national BLL estimated with data from Phase 2 of NHANES III (conducted during October 1991-September 1994), which indicate that BLLs in the U.S. population aged > or = 1 year continued to decrease and that BLLs among children aged 1-5 years were more likely to be elevated among those who were poor, non-Hispanic black, living in large metropolitan areas, or living in older housing.