Long-term effects of radiotherapy in childhood and adolescence. The records of 50 selected pediatric patients who were treated and followed at M. D. Anderson Cancer Center were reviewed to study the late effects of nonsurgical treatment of cancer in children. There were 26 girls and 24 boys ranging in age between 2 months and 16 years. Patients with head and neck cancer received chemotherapy and radiotherapy for rhabdomyosarcoma (n = 27), retinoblastoma (n = 8), or nasopharynx cancer (n = 2). Median follow-up was 13 years. The most severe side effects were noted in the fields of radiation and included hypoplasia of the jaw, orbit, or hemi-face with varying degrees of atrophy of the overlying soft tissues. A wide range of endocrine, dental, and psychologic abnormalities was also documented. Since 1 in every 1,000 adults older than 20 years today is likely to be a survivor of childhood cancer, recommendations are made for this "new" class of patients whom the head and neck surgeon will be seeing in the future. 