We report on 49 patients younger than 18 years at diagnosis, of 776 patients with thyroid cancer, seen in our institution in the last 17 years. Female/male ratio was 2.2:1. Histologic type was papillary in 44, follicular in 4, and medullary in 1. Initial treatment was near-total thyroidectomy with or without neck dissection. Surgical complications (vocal cord palsy, permanent hypoparathyroidism, or both) were found in 25 patients and were usually associated with more advanced primary tumors. At surgery, node metastases were present in 73% of the patients and lung metastases, detected by chest x ray films, in 6%. Patients were treated with thyroid suppressive therapy and, except the one with medullary cancer, with radioiodine (131I) therapy. After a mean follow-up of 7.7 +/- 4.4 years (range, 1 to 17 years), one patient with lung metastases died of respiratory failure. Of 36 patients who have been followed up more than 4 years, 22 (61.1%) are now cured, and 14 have metastases (to lymph nodes, 2; to nodes and lung, 10; and to lung, 2). Since 1977 serum thyroglobulin (Tg) was used routinely as a tumor marker for differentiated thyroid cancer. After operation, Tg was elevated in all patients both not receiving (mean +/- SE, 902 +/- 380 ng/ml) and receiving (44 +/- 15 ng/ml) suppressive therapy; after 131I treatment, serum Tg dropped to 104 +/- 50 and 7.3 +/- 1.7 ng/ml, without and with suppressive therapy, respectively. Of 11 patients with lung metastases treated with 131I, respiratory function, as assessed by means of spirometry, was normal in three, mildly reduced in six, and severely impaired in two (including the one who died). In conclusion, our study indicates that thyroid cancer in young patients is rather advanced at initial examination and usually associated with node and, less frequently, lung metastases. Total thyroidectomy, radioiodine treatment, and thyroid suppressive therapy represent an effective combination of treatments for this disease and allow a good quality of life. The most serious adverse effect is represented by the high incidence of surgical complications and by pulmonary restrictive disease in relation to lung metastases.