Childhood neoplasms provide a fertile field for epidemiological research and afford a unique opportunity for studying possible mechanisms of carcinogenesis. The present study reviews 1881 malignant childhood neoplasms in children less than 15 years of age seen in the University College Hospital, Ibadan during an 18-year period. The male-to-female ratio was 1.4:1 and modal age of occurrence was 10 years. The most common childhood neoplasms were lymphomas (45.4%), retinoblastomas (9.7%), and malignant renal neoplasms (8.5%). Burkitt's lymphoma constituted 92% of all lymphomas and 37% of all childhood tumors. Comparison of two clinicopathological studies of childhood cancer in Ibadan between 1960-1972 and 1973-1990 revealed a dramatic upsurge in the relative frequencies of intracranial neoplasms, leukemias, renal neoplasms, and retinoblastomas, with a decline in the relative frequencies of bone neoplasms and Burkitt's lymphoma during the latter period. Whether these changes reflect actual changes in the distribution of childhood cancer in the local population will require further study.