We reviewed a group of 30 patients with Hashimoto's thyroiditis who underwent thyroidectomies for suspicion of cancer. A prominent nodule was present in all of the patients; compression symptoms were present in 13 and pain in the thyroid in six. The nodule was cold on scan in 21 patients. Lack of responsiveness to suppressive therapy or nodule enlargement occurred in 18 patients. In addition to the nodule, operative findings included adherence to surrounding tissues in seven patients, lymphadenopathy in seven, increased vascularity in four, and extension to distant cervical structures in two. Pathologic findings in the nodule were similar to those in the rest of the gland; they consisted of lymphocytic infiltration, fibrosis, and variable follicular size. Examination of lymph nodes demonstrated lymphoid hyperplasia. We emphasize the similarities between chronic thyroiditis and carcinoma of the thyroid; the occasional coexistence of these two conditions stresses the need for newer methods in the differential diagnosis.