One in 600 children 0-16 years of age develop cancer, and 60% to 70% of them are cured. Projection of the data indicates that by the turn of the century, 1 of every 900 individuals between the ages of 16 and 44 years will be a cancer survivor. In the adult population, carcinogens and irradiation play a major role in oncogenesis. In the pediatric population other factors are probably dominant. Children of low socioeconomic groups, with nutritional deficiencies, are more exposed to viral infections at a very early age and have a greater chance of developing tumors such as Burkitt lymphoma or mixed cellularity Hodgkin disease. Other factors such as hormone-assisted conception or in vitro fertilization may have carcinogenic potential, although this has yet to be determined. Maternal diet during pregnancy, especially low folic acid consumption periconception, may have bearing on the fetus's risk of developing malignancy. The hazards of exposure to electric and magnetic fields from high-voltage transmission lines, home electric appliances, video display terminals, or residence near nuclear plants, although very doubtful, are included in the list of cancer promoters in children. Activated oncogenes, mutated suppressor genes, mismatch repair genes, nucleotide excision genes, and loss of imprinting genes are beginning to evolve as important factors in carcinogenesis. The more in-depth information on genetic and environmental factors should provide new data on the evolution of pediatric tumors and possibly on their prevention.