To determine the necessity of performing a hemithyroidectomy in patients who require a total laryngectomy, the pathologic reports and clinical courses of 261 patients who underwent total laryngectomy were reviewed. Twenty-four percent of the specimens demonstrated transcartilaginous invasion, with the highest incidences occurring in glottic (31 percent) and subglottic (60 percent) tumors. Epidermoid tumor invading the thyroid gland occurred in 5 percent of the specimens. All of these showed invasion by direct extension, were palpable at the time of surgery and were associated with transcartilaginous invasion. Ninety percent of these tumors were primarily glottic or subglottic and 70 percent demonstrated subglottic extension greater than 1.5 cm. Furthermore, the prognosis of patients with tumorous invasion of the thyroid gland was dismal, with local recurrence or distant metastasis occurring within 10 months of curative resection. In patients who had laryngectomies, hypothyroidism was found in 70 percent of those who underwent radiotherapy and hemithyroidectomy, in 38 percent of those who underwent radiotherapy alone, in 23 percent of those who underwent hemithyroidectomy alone, and in 20 percent of those who did not undergo hemithyroidectomy or radiotherapy. Based on these results, we advocate ipsilateral or total thyroidectomy for palpably suspicious thyroid glands seen intraoperatively, subglottic tumors, glottic tumors with more than 1 cm of subglottic extension, T4 endolaryngeal tumors with transcartilaginous invasion, and T4 pyriform sinus tumors.