Between 1969 and 1977, 269 patients submitted to thyroidectomy were treated exclusively with radioiodine according to a standardized irradiation scheme. The patients were observed during thirteen years. 195 patients were free of metastases at the time of the first therapy, whereas 74 patients had lymph node metastases or remote metastases. The survival rates of the total group were 89% (five years) and 76% (10 years), respectively. Patients with regional lymph node metastases had a ten-year survival rate of 74%. The fourty patients suffering from remote metastases had a five-year survival rate of 75% and a ten-year survival rate of 40%. Patients who were in stage T3 at the moment of diagnosis had a survival probability of 74% for five years and of 59% for eight years. None of these patients presented with remote metastases during the follow-up period. Taking into consideration these results and the small rate of complications, we are of the opinion that a routine combination therapy with external post-irradiation is not necessary.