A retrospective 10-year review of thyroid function in 144 patients treated for cancer of the head and neck by radiation therapy, surgery, and combined surgery and radiation therapy was done. In five patients, hypothyroidism had been found in the posttreatment period. Two of them had developed a pharyngeal fistula resistant to intensive local care and surgical procedures, and a third patient had edema and necrosis of the skin flap. The five hypothyroid patients reported here have all been treated for laryngeal malignancy. In any other group of patients treated for head and neck malignancies studied within this article, we did not find clinical or chemical signs of thyroid hypofunction. Our report stresses the importance of periodic evaluation of thyroid function in patients who underwent irradiation of the neck or combined therapy for malignancy in the neck, even if they were clinically euthyroid. Hypofunction may be more frequent than generally recognized after multimodality treatment, and hormonal replacement therapy may be the keystone in curing rebellious pharyngeal fistula and shortening the disabled state of the patient.