We sought to identify modifiable determinants of elevated blood lead levels in preschool children; to compare the current situation with past information; to determine historical trends in environmental lead contamination in Trail; and to find a basis for identifying appropriate precautions and protection against future lead exposure. In Phase 1, blood samples were drawn from all children aged 2 to 5. In Phase 2, children in the highest and lowest quartile of blood leads were surveyed by questionnaire. Environmental samples of drinking water, paint, housedust, soil and vegetables were taken from their residences, and soil samples were collected from nearby parks. The average blood lead level was 13.8 micrograms/dl, range 4 to 30 micrograms/dl. This is approximately 40% lower than in 1975, when a previous survey was done, but is high compared to other places in Canada. The study of environmental determinants of lead revealed that soil lead levels and, secondarily, housedust lead levels are the principal determinants of high blood lead. Children with high blood leads also tended to concentrate in neighbourhoods near the lead-zinc smelter.