The aim of this study was to evaluate exposure and health outcome of children living close to industrial sources. Exposure and health outcome was assessed in nearly 1000 children at school beginner age living in the vicinity of industrial sources of three different hot spots (Duisburg North, Duisburg South and Dortmund Hörde) and in a rural area of North Rhine Westphalia (NRW), Germany. The cross-sectional study was undertaken between March and May 2000. Exposure assessment comprised modelling of ambient air quality data and human biomonitoring (HBM). Depending on the site-specific contaminants, HBM included the measurement of PAH (polycyclic aromatic hydrocarbons) and benzene metabolites in urine as well as heavy metals in blood and urine. Markers of early effects were DNA strand breaks as measured by the comet assay in lymphocytes and excretion of alpha-1-microglobuline and N-acetyl-beta-D-glucosamidase in urine. Health outcome was assessed by questionnaire, lung function test, dermatological examination as well as by RAST (radioallergosorbent test), patch tests and prick tests. The influence of exposure variables on biomarkers and health outcome was measured by means of multiple linear and logistic regression analysis. The most striking results were as follows. Children living close to a coke oven plant (Duisburg North) had increased levels of PAH metabolites in urine, and DNA exposure was increased. Children living at the Dortmund Hörde hot spot (increased chromium and nickel ambient air levels from a steel mill) revealed a high prevalence of allergic sensitizations. Sensitization, especially against nickel, was associated with the current internal nickel exposure, and nickel in ambient air was positively associated with the frequency of allergic symptoms. Children from the hot spot areas had increased specific airway resistance and total lung capacity as compared to those of the reference area. In Duisburg North particularly, specific airway resistance and total lung capacity significantly increased with increasing TSP (total suspended particulate). The only positive associations between external and internal exposure were found between benzo[a]pyrene in ambient air and 1-hydroxypyrene in urine, and between lead in ambient air and in the blood of the children. It is concluded that despite improvements of the general air quality during the last decades, living in the vicinity of industrial sources results to some extent in increased internal contaminant exposure and in effects on health outcome. Still ongoing studies are aimed to find out whether the increased PAH and DNA exposure of children from Duisburg North had decreased after the coke oven plant had been shut down in 2003, and if the striking results on the high prevalence of allergic sensitization can be confirmed by introducing an expanded cross-sectional study at four hot spots with increased chromium and nickel ambient air levels.