The results of therapy are reported in 296 patients with histologically proven epidermoid carcinoma of the tonsillar fossa; 127 were treated with irradiation alone (5,500 to 7,000 cGy), 133 with preoperative radiotherapy (2,000 to 3,000 cGy) or were initially planned for preoperative irradiation but treated with radiotherapy alone, and 36 with postoperative irradiation (5,000 to 6,000 cGy). The operation in all but 4 patients consisted of an en bloc radical tonsillectomy with ipsilateral lymph node dissection. Actuarial 5-year no evidence of disease (NED) was as follows: survival rates for patients with T1 tumors, 76%; T2, 54%; T3, 45%; and T4, 20%. Patients with no cervical lymphadenopathy or with a small metastatic lymph node (N1) had better relapse-free survival (60% to 70% at 5 years) than those with large or fixed lymph nodes (30% to 40%). Primary tumor recurrence rate in the T1-T2 groups was about 20% in patients treated with irradiation and surgery and 30% for those treated with irradiation alone (difference not statistically significant), 30% in patients with stage T3 lesions in all treatment groups, and 33% in patients with T4 disease treated with surgery and postoperative irradiation compared to 52% with irradiation alone (p = 0.03). The overall recurrence rate in the neck was about 20% for the N0 patients, 25% for N1, and 30% for those with N2 and N3 cervical lymph nodes in the 4 treatment groups. The incidence of contralateral neck recurrences was about 8% with the various treatment modalities.(ABSTRACT TRUNCATED AT 250 WORDS)