PURPOSE: For the control of childhood leukemia, of which the mortality is still high, the basic data for the incidence has a great importance. The authors analyzed the data from 133 new patients with childhood leukemia between 1996-2000 in Busan, Korea. METHODS: The data were obtained from 133 new cases(87 males and 46 females from 0 to 15 years old) of childhood leukemia who were residents of Busan and who were admitted to the 4 university hospitals and 11 general hospitals from 1996 to 2000. RESULTS: The total number of the new childhood leukemia patients was 133 between 1996-2000; the average annual number of new patients was 26.6. The age-and-sex adjusted annual incidence rate (/100,000) was in the range of 2.37-4.53(male 2.47-5.29, female 0.76-3.36) with an average of 3.29 (male 4.05, female 2.43). Age-specific annual incidence rate(/100,000) was 3.78 in the 0-4 year age group, 3.51 in the 5-9 year age group and 3.08 in the 10-14 year age group. Of the major types of childhood leukemia, the distribution of ALL was average 71.4%, of AML 23.3%, and of CML 4.5%. Of the major types of leukemia by age range, ALL showed highest in the 5-9 year age group, while AML in 0-4 and 10-14 year age groups. Sex-ratio(male to female) of major type of leukemia was 1.97 : 1 and 1.21 : 1, in ALL and AML groups, respectively, while all were male in CML. CONCLUSION: The average age-and-sex adjusted annual incidence rate(/100,000) of childhood leukemia in Busan from 1996 to 2000 was 3.29. Compared to data in related articles, this data suggests a steady increase in the incidence of childhood leukemia in the Busan area over the last 20 years since 1981.