Objective To analyze the prevalence of asthma and asthma related symptoms among children aged 0-14 years in three Chinese cities and to obtain a crude estimation of the trend of childhood asthma prevalence in China. Methods A cross-sectional, population-based survey of prevalence of asthma was conducted in children aged from 0 to 14 years in 3 major cities of China (Beijing, Chongqing, and Guangzhou) with different geographic locations. All the subjects were randomly selected by a multi-stage sampling method. Three to five schools and kindergartens in 2 urban districts in each city were randomly selected for the survey, and a validated questionnaire that included the core questions of the International Study of Asthma and Allergies in Childhood, Phase III questionnaire and several additional questions were used. All questionnaires were completed by parents or guardians of the selected children. Children whose parents responded affirmatively to the question" Has your child ever been diagnosed as asthma by a doctor" were recognized as victims of asthma. Results The prevalence of asthma in Beijing, Chongqing, and Guangzhou was 3.15%, 7.45%, and 2.09%, respectively. These values were significantly higher than those obtained 10 years ago in the national epidemiological survey in 2000 which used the same method of investigation and the same diagnotic criteria (chi(2)=3.938, P=0.047; chi(2)=73.506, P <= 0.001; chi(2)=11.956, P=0.001, in each city). Of the asthmatic children 57.21%, 69.91%, and 60.00% had their first attack before the age of 3 in Beijing, Chongqing, and Guangzhou, respectively. Wheezing was the primary clinical manifestation for all asthmatic children, followed by persistent cough and repeated respiratory infections. Both the prevalence of asthma and asthma-related symptoms were statistically higher in males than in females. Conclusion The prevalence of childhood asthma is statistically higher than that 10 years ago in the three Chinese cities.