An investigation has been carried out of the blood lead levels of children resident in three different municipalities of Umbria: Corciano, selected as a control area; Perugia, the largest town in Umbria (approx. 150,000 inhabitants), with intense automobile traffic; and Deruta a town in which there is a flourishing ceramic industry. The mean blood lead levels were found to be higher in children in Perugia (96 micrograms/l) and Deruta (97 micrograms/l) with respect to Corciano (83 micrograms/l); in Deruta the mean blood levels were raised in those children whose families are occupationally exposed to lead (107 micrograms/l). The concentration of lead in the air in Deruta was higher than in Corciano (0.19 vs 0.11 microgram/m3, respectively). The lead concentrations in house dust were higher in Deruta (2.8 micrograms/m2) than in Corciano (0.8 microgram/m2) and the difference was greater in the houses were the inhabitants were exposed to lead in factories (2.7 micrograms/m2) or in workshops which were adjacent to the houses (4.7 micrograms/m2). The blood lead levels of children included in this study have been compared with those obtained during a similar investigation in 1978. Over the last eight years primary school children in Corciano and Deruta have shown a marked reduction in blood lead levels (greater than 50%). This improvement should not lead to false optimism: in fact, it is impossible to establish the blood lead level at which no adverse effects are induced, especially in children. Numerous studies suggest that even sub-clinical levels of lead can cause alteration in heme synthesis, peripheral nervous system, kidney, immune system, skeleton and growth. Furthermore, with regard to the central nervous system, low blood lead levels can provoke neuropsychological deficits, which can result above all, in a decreased I.Q., and behavioural alterations.