Blood lead levels were determined on a random sample of persons in all age groups living near a lead-emitting smelter in El Paso, Texas. A blood lead level of greater than or equal to 40 mug per 100 ml, which was considered indicative of undue lead absorption, was found in 53 per cent of the children one to nine years old living within 1.6 km of the smelter and in 18 per cent of those from 1.6 to 6.6 km; beyond that distance in older persons levels were lower. Children in the first 1.6 km with blood levels of greater than or equal to mug per 100 ml were exposed to 3.1 times as much lead in dust as children there with lower blood values (6447 vs 2067 ppm). There was also airborne lead exposure (8 to 10 mug per cubic meter, annual mean). Paint, water, food, and pottery were less important as sources. The data suggest that particulate lead in dust and air accounted for most of the lead absorption in El Paso children. The smelter was the principal source of this lead, especially within 1.6km of itself.