Experimental and observational data has long implicated automobile exhaust from leaded petrol as a major source of human lead exposure. The present study evaluates the association of individual traffic exposure with individual lead absorption. A case-referent study was carried out on 1302 out of 2412 children in the municipality of Aarhus - Denmark. Shed deciduous teeth were matched for sex and socioeconomic status. Individual lead sources were assessed by an interview. Information on former addresses and the data of address change was obtained as was information on the daily number of cars driving on all roads of the city. A traffic index was constructed describing the traffic density at the home. An association between high lead and high traffic density was found in the children at the age of 6 months to 2 years. This relationship was of a dose-response nature. The association was not account for by other possible major sources.