Squamous cell carcinoma (SCC) of the thyroid is thought to be rare. However, SCC not infrequently occurs in conjunction with other histologic types of tumor. We reviewed 67 thyroid cancer autopsy cases obtained from two institutions from 1969 to 1981 and from 1975 to 1992, respectively. SCC was found in 19 cases (28.4%): 2 SCCs as the only malignancy and of uniform histologic type, 9 cases of tumors mixed with papillary carcinoma, and 8 cases of SCC mixed with papillary and anaplastic carcinomas. In only four of these cases was the SCC component found in the surgical specimens. These results indicate that the presence of SCC component is more likely to be found at the later stage of the disease.