The risk of late effects of cancer treatment in children is higher than that after treatment during adulthood. The late effects of chemotherapy are proportional to the dosage and those of irradiation to the size of the radiation field, fractionation and dose. Irradiation may lead to impaired growth of bone and soft tissues, cranial irradiation to pituitary deficiencies, alopecia and impaired cognitive function, irradiation of the neck to altered thyroid function, thoracic irradiation to diminished pulmonary function and cardiovascular morbidity, radiation therapy of the abdomen to infertility in females, impaired renal function and chronic enteritis. Chemotherapy-induced damage is more organ-specific. Well-known cardiotoxic agents are the anthracycline derivatives. Restricted pulmonary function is seen after treatment with bleomycin and nitrourea derivatives. Several antineoplastic agents are gonadotoxic in men. Nephrotoxic agents are cisplatin and ifosfamide. The cumulative relative risk of developing a second primary neoplasm is 3,8-6,9 after a follow-up period of 25 years. Alkylating agents and the topoisomerase inhibitors are known to increase the risk of haematologic malignancy, while radiation therapy is associated with bone, soft tissue, thyroid, breast, brain and gastrointestinal malignancies.