Purpose:The first Korean national population-based cancer registry using nationwide hospital-based recording system and the regional cancer registries provided the source to obtain national cancer incidences for the period 1999~2001.M aterials and Methods: The incidence of cancer in Korea was calculated based on the Korea Central Cancer Registry database, data from additional medical record review survey, the Regional Cancer Registry databases, site-specific cancer registry databases, and cancer mortality data from the Korea National Statistical Office. Crude and age-standardized rates were calculated by sex for 18 age groups.Results: The overall crude incidence rates (CR) were 247.3 and 188.3 per 100,000 for men and women and the overall age-standardized incidence rates (ASR) were 281.2 and 160.3 per 100,000, respectively. Among men, five leading primary cancer sites were stomach (CR 58.6, ASR 65.6), lung (CR 42.1, ASR 50.9), liver (CR 41.9, ASR 44.9), colon and rectum (CR 24.2, ASR 27.3) and bladder (CR 7.7, ASR 9.2). Among women, the most common cancers were stomach (CR 30.8, ASR 25.8), breast (CR 25.7, ASR 21.7), colon and rectum (CR 19.6, ASR 16.7), uterine cervix (CR 18.4, ASR 15.5), and lung cancer (CR 15.1, ASR 12.4). In 0~14 age group, leukemia was most common for both sexes. For men, stomach cancer was most common in 15~64 age group, but lung cancer was more frequent for over 65 age group. For women, thyroid cancer in 15~34 age group, breast cancer in 35~64 age group, and stomach cancer in over 65 age group were most common for each age group. The proportions of death certificate only were 7.5% for men and 7.4% for women.Conclusion: This is the first attempt to determine the national cancer incidence and this data will be useful to plan for research and national cancer control in Korea.