Eleven patients under 16 years of age, 5 males and 6 females were diagnosed with thyroid carcinoma in our hospital between 1974 and 1992. Median age at diagnosis was 9.5 years (range: 5.2-15.7 years). The presenting sign was a single thyroid nodule in 5, multiple thyroid nodules in 1, cervical adenopathy in 3, and thyroid nodules in conjunction with cervical adenopathy in 2 patients. Histological diagnosis was papillary carcinoma in 5 cases, follicular carcinoma in 2, mixed papillary-follicular carcinoma in 3, and anaplastic carcinoma in one. Only 4 patients had no extrathyroidal metastases at diagnosis. All but one subjects underwent total thyroidectomy, either one-staged or two-staged. If metastases were present, ablative radio-iodine therapy followed. Two patients died within a few months, one from complications of lung metastases, another from diffuse spread of anaplastic carcinoma. Two patients were lost to follow up; 7 patients have been followed for 9.0-18.0 years. Of these, one patient with initial lung metastases has had six recurrences which were success fully treated each time with radio-iodine although thyroglobulin levels remained elevated; another patient who had an initial subtotal thyroidectomy incurred a relapse 12 years later during pregnancy but is doing well now after more intensive surgery. We propose that children with differentiated thyroid carcinoma should undergo total thyroidectomy and selective lymph node extirpation by a skilled surgeon followed by whole body radio-iodine scan and ablative radio-iodine treatment if necessary. Plasma thyroglobulin can then be used as a tumour marker and suppressive levothyroxine does should be given.