Within an environmental health study, dermatologic examination of 1273 pre-school-age children (5-7 years old) was carried out in selected areas of East (n = 287) and West (n = 987) Germany in spring 1991. On the basis of comparable genetic background, the influence of a different exposure to air pollutants on the manifestation of atopic diseases was investigated. Halle an der Saale (East Germany) and Duisburg (North/South) as well as Essen (West Germany) were chosen as polluted study areas, whereas the countryside town of Borken (West Germany) served as a control region. Outdoor pollution with particles and SO2 was significantly higher in Halle an der Saale. Of the total study group, 12.9% suffered from atopic eczema at the time of examination. The prevalence was highest in East Germany (17.5%; adjusted odds ratio [OR] 1.39, confidence intervals [GI] 0.77-2.52, compared to Borken). The reported frequencies of hay fever and asthma in the total study population were 2% and 1.3%, respectively, without significant differences between study sites. Some 34.7% of the children showed at least one positive skin prick test reaction; significantly (P < 0.001) higher sensitization rates were obtained in western regions (Essen, Duisburg-South) than in the control region (Borken) and East Germany. Multivariate analysis of the prevalence of atopic eczema showed associations with parental predisposition (OR 1.52, CI 1.03-2.25), sex (for boys, OR 0.63, CI 0.43-0.92), location (Duisburg-South vs Borken OR 0.52, CI 0.30-0.96), month of investigation (May vs April, and March vs February OR 0.55, CI 0.37-0.81), contact with rabbits (for girls, OR 2.90, CI 1.36-6.19), animal fur in bedrooms (2.17, 1.01-4.67), indoor use of gas without hood (1.68, 1.11-2.56), and distance of homes from a busy road (< 50 m 1.71, 1.07-2.73). Nonsignificant associations were observed for history of helminthic infections (OR 1.61, CI 0.98-2.64) and high parental education level (OR 1.83, CI 0.83-4.02). In East and West Germany, atopic eczema seems to follow a course different from that of respiratory allergic diseases and specific sensitization, a fact which underlines the need for a differentiated analysis.