OBJECTIVES--To study the potential impact of environmental exposure to petrol lead, residential area, age, sex, and lead exposing hobby, on blood lead concentrations (BPb) in children. METHODS--In the south of Sweden, yearly from 1978-94, BPb was measured in 1230 boys and 1211 girls, aged between 3 and 19 (median 10; quartiles 9 and 12) years. RESULTS--For the samples of 1978, the geometric mean (GM) was 67 (range 30-250) micrograms/l in boys and 53 (18-161) micrograms/l in girls, whereas the corresponding GMs for 1994 were 27 (12-122) and 23 (12-97) micrograms/l. The sex difference was present only in children over eight. Moreover, residential area affected BPb; in particular, children living near a smelter area had raised BPbs. There was a clear ecological relation between BPb (adjusted GM) and annual lead quantity in petrol sold in Sweden, which was estimated to be 1637 tonnes in 1976 and 133 tonnes in 1993 (P