The records of 216 patients with squamous cell carcinoma of the oral cavity, oropharynx, and hypopharynx treated by surgery alone were reviewed. Frozen section control at the time of the surgical procedure was used to evaluate the margins of the excision. Findings at frozen section were correlated with local control and survival. The inability of the surgeon to obtain clear margins by frozen section for whatever reason resulted in a very high incidence of local recurrence and death. The fact that the patient's tumor could be removed with free margins at the time of surgery did not guarantee long-term success, although the frozen section technic did prove to be reliable and an effective tool for evaluating the patient's prognosis and the efficacy of the surgical procedure.