This is a retrospective analysis of 143 patients with histologically confirmed epidermoid carcinoma of the nasopharynx treated with definitive irradiation. Patients were treated with a combination of Cobalt-60, 4 to 6 MV X rays, and 18 to 25 MV X rays to the primary tumor and the upper necks, excluding the spinal cord at 4000 to 4500 cGy to total doses of 6000 to 7000 cGy. At 10 years the actuarial primary tumor failure rate was 15% in T1, 25% in T2, 33% in T3, and 60% in T4 lesions. The corresponding failure rate in the neck was 18% for N0, 14% for N1, and 33% for N2 and N3 lymphadenopathy. The incidence of distant metastasis was related to the stage of the cervical lymphadenopathy: 16% in patients with N0-N1 nodes compared with 40% in the N2-3 node group. The actuarial 10-year disease-free survival rate was 55% to 60% for T1-3N0-1 tumors, 45% for T1-3N2-3 tumors, 35% for T4N0-1, and 20% for T4N2-3 lesions. The overall 10-year survival rate was about 40% for patients with T1-2N0-1 tumors, 30% for those with T3 any N stage tumors, and only 10% for the patients with T4 lesions. Multivariate analysis showed that tumor stage and histological type, cranial nerve involvement, patient age, and doses of irradiation to the nasopharynx were significant prognostic factors for local/regional tumor control. Increasing doses of irradiation resulted in nasopharynx tumor control in 80% of the patients receiving 6600 to 7000 cGy and 100% of those receiving over 7000 cGy in the T1, T2, and T3 tumors. However, the tumor control rate did not rise above 55% even for doses over 7000 cGy in the T4 lesions. Local tumor control was higher in patients who had simulation (55/78 = 71%) compared with those on whom simulation was not performed (34/61 = 56%) (p = 0.10). Moreover, patients with more than 75% of the reviewed films judged as adequate had 69% primary tumor control (66/96) compared with 53% (23/43) for those with fewer than 75% adequate portal films (p = 0.07).