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 that observed in many other white populations. However, the incidence rates of leukemia, lymphomas, neuroblastomas, and soft-tissue tumors were somewhat lower than the figures reported in the Third National Cancer Survey of the United States.