Between 1953 and 1970, 2,605 malignant tumors in children under 15 years of age were reported to the Finnish Cancer Registry, a population-based registry that covers the whole country (population, 4.6 million). The mean annual age-adjusted incidence rates per million were 128 in males and 108 in females. The most common neoplasms were leukemia (age-adjusted incidence rates, 43.7 in males; 34;7 in females), brain tumors (26.4 in males, 22.8 in females), renal tumors (10;0 in males, 9.1 in females), lymphomas (10.8 in males, 5.3 in females), and bone tumors (5;3 in males, 5.1 in females). This distribution is roughly the same as the observed in many other white populations. However, the incidence rates of leukemia, lymphomas, neuroblastomas, and soft-tissue tumors were somewhate lower than figures reported in the Third National Cancer Survey of the United States.