This study tracks the temporal changes in prevalence of childhood and adolescent overweight and obesity in different regions of China from 1985 to 2005. Using a series data of the Chinese National Survey on Students Constitution and Health, we compared the temporal changes over a 20-year period of the prevalence of overweight and obesity among ten regions in China for school-aged children between 7 and 18 years of age. Large disparities in the temporal changes of obesity prevalence exist in different regions of China. North coastal residents, especially those of the upper socioeconomic status, had the earliest and largest increase in prevalence. Similar increases then followed successively in other regions of upper, moderate and low socioeconomic status, and finally in the affluent rural regions. No significant increase was found in the developing rural areas. Regions where the obesity epidemic occurred late also began to show rather rapid increases in prevalence in recent years. In 2005, the national estimates indicated that 7.73% of Chinese youth are overweight and 3.71% of them are obese, representing an estimated 21.37 million Chinese children (13.43 million boys and 7.94 million girls).