Thirty-eight cases of fatal thyroid carcinoma (TC) occurred in a demographically well-defined area of, on an average, 243,000 inhabitants during an 18-year period, corresponding to an annual mortality rate of 0.9 per 100,000. The mortality rate did not change significantly during the period of investigation. All diagnoses were based on autopsy findings and were revised histologically. Ten cases were found to have papillary cancer, 10 follicular, 4 medullary, and 14 anaplastic. The survival time ranged between 0 and 27 years; two patients with medullary cancer died later than 10 years after diagnosis; none of the remaining patients died from the malignant disease later than 9 years after TC diagnosis. Nine of the anaplastic tumors contained elements of differentiated TC, and five patients who died from anaplastic cancer had had a history of goiter for more than 2 years. Insufficient surgical treatment (procedures less than lobectomy) was considered partially responsible for the fatal outcome in 3 of 14 surgically treated patients. Five deaths could be ascribed to complications to treatment. Two patients died postoperatively, two died from late effects of irradiation therapy, and one died in a coma caused by insufficient replacement therapy. The TC diagnosis was a postmortem surprise finding in ten cases.