Six hundred and five persons, randomly selected from a cohort of 2400 patients who had been irradiated 16-46 yr previously for benign diseases in the head and neck region, were traced, recalled and examined for radiation-associated tumours. Three hundred and sixty-seven patients were alive, 179 had died and 66 had emigrated. Two hundred and fifty-seven patients were clinically examined, 87 refused or were not able to participate and 16 could not be contacted. Eighteen of the clinically examined patients had been or were being treated for 20 skin carcinomas with a mean latency of 37 yr. In this group only 7 carcinomas of the thyroid gland were observed, with a mean latency of 38 yr. Eleven carcinomas of the skin and 3 of the thyroid gland were reported in the group which was examined by means of questionnaires. The observed number of carcinomas of the skin is higher than expected according to the dose-effect relationship of UNSCEAR, whereas the number of carcinomas of the thyroid gland is lower. It is concluded that there might be less difference in susceptibility for the induction of tumours by ionizing radiation between the skin and the thyroid gland than is commonly assumed.