Cancer is becoming a more important health problem in Taiwan with aging of populations and changes in lifestyles. This indicates that a population-based cancer registration database is essential to providing informative data on cancer prevention and policy setting. The Taiwan Cancer Registry was launched in 1979 and all reporting hospitals were mandated to submit cancer data to the central cancer registry following the enactment of the Cancer Control Act in 2003. The National Health Insurance program in Taiwan has successfully provided quality health care, comprehensive benefits and convenient access to treatment. Most cancers had a rapidly increasing incidence after the initiation of the NHI program. However, cancer incidence rates of nasopharynx of both genders slightly decreased throughout the entire period and incidence of stomach cancer of both genders and cervical cancer of females declined beginning in 1995. For childhood cancers, the major types of leukemia, lymphomas, central nervous system neoplasms and other epithelial neoplasms for males and females accounted for nearly 55% of all types. This study presents for the first time the secular changes and age patterns in the incidence of childhood cancer using national cancer data.