Several regional cross-sectional studies have shown a consistently higher prevalence of respiratory disorders in children with exposure to total suspended particulates (TSP) than in children living in less polluted areas. The aim of the present study was to investigate the temporal changes in the prevalence of nonasthmatic respiratory symptoms and diseases in children living in three areas of East Germany during a phase of strong improvement in ambient air quality. Groups of 2,470 and 2,814 school children between 5 and 14 yr, respectively, participated in two regional cross-sectional studies in 1992-1993 and 1995-1996. In the three areas (Hettstedt, Bitterfeld, and Zerbst) examined in the study, the annual mean TSP decreased from 65, 48, and 44 microg/m(3), respectively, in 1993 to 43, 39, and 36 microg/m(3) in 1995. In the same time interval, the crude prevalence of bronchitis in the three respective areas decreased from 62%, 52%, and 50% to 47%, 40%, and 39%. During the 3-yr period between the two regional studies, prevalence decreased significantly for bronchitis (odds ratio [OR]: 0.55; confidence interval [CI]: 0.49 to 0.62), for otitis media (OR: 0.83; CI: 0.73 to 0.96), for frequent colds (OR: 0.74; CI: 0.64 to 0.86), and for febrile infections (OR: 0.76; CI: 0.66 to 0.88) after adjustment for several potential predictors. In conclusion, we found that the prevalence of nonasthmatic respiratory symptoms decreased from the first period to the second period in all three study areas.