Survival from cancer in childhood and adolescence was studied in a population-based series of 8312 cases in children aged 0-19 years notified to the Danish Cancer Registry during 1943-87. During the first period (1943-72), 5-year survival rates from all malignant neoplasms increased from 23% (1943-52) to 33% (1963-72). The greatest improvement was seen during the period 1973-87 when 5-year survival rates reached 64% (1983-87). Between 1973-77 and 1983-87, 5-year survival rates increased from 32% to 62% for leukaemia, from 40% to 70% for acute lymphoblastic leukaemia, from 35% to 54% for non-Hodgkin's lymphoma, from 50% to 66% for central nervous system neoplasms and from 25% to 49% for bone tumours. An improvement in 5-year survival rates from Wilms' tumour was seen between 1960 (19%) and 1980 (81%). Up to 1972, the 5-year survival rate from germ-cell neoplasms was approximately 40%; among patients diagnosed in 1983-87, 76% survived for 5-years. Annual lethality decreased by 2.5% for all malignant neoplasms in 1943-72 and by 4.4% in 1972-87. Lethality was similar for boys and girls during the period 1943-72, but was significantly lower for girls subsequently. A marked effect of age at diagnosis was seen in the early registration period, where lethality rate for the age group 0-9 years was substantially higher compared with that in the age group 10-19 years. This inequality persisted only for children less than 2 years of age at the time of diagnosis in the later period.