The overall cure rate for childhood cancer is now over 60%, and for some tumors it is over 90%. It has been estimated that by the year 2000 at least 1 in 1000 young adults will have been cured of childhood cancer. This improved survival has stimulated great interest in the adverse late effects of radiotherapy and cytotoxic chemotherapy on growth and the endocrine system. Radiation therapy may directly impair hypothalamic, pituitary, thyroid, and gonadal function, or alternatively, it may induce the development of hyperparathyroidism and thyroid adenomas or carcinomas. Cytotoxic chemotherapy may damage the gonad, and both irradiation and cytotoxic chemotherapy may interfere with the normal growth of bone. A variety of clinical presentations which require endocrine expertise in management may result from these complications of treatment, including short stature, failure to undergo normal pubertal development, precocious puberty, hyperparathyroidism, hypothyroidism, thyroid tumors, gynecomastia, infertility, and varying degrees of hypopituitarism.