From April 1986 to May 1989, 112 patients seen at a single institution with previously untreated squamous cell oropharynx carcinoma, Stages III and IV, were randomly assigned to 66 Gy in 33 fractions of 2 Gy each (conventional RT) versus 70.4 Gy in 64 fractions of 1.1 Gy given twice a day with a minimal interfraction interval of 6 hours (hyperfractionated RT). The overall time for both arms was 6 1/2 weeks. Patients were stratified by site (base of the tongue vs others), T stage (T1/T2 vs T3 vs T4), N stage (N0/N1 vs N2 vs N3), and lymphnode size (less than 6 cm vs greater than 6 cm). As of January 1990, an analysis was performed in 98 patients (8 patients in the conventional arm and 6 in the hyperfractionation not included). The groups were balanced by age, performance status, stage, and site of the primary disease. The median follow-up time was 25 months. The probability of complete loco-regional response was 62% in the hyperfractionation arm and 52% for the conventional fractionation (p = 0.28). There was no difference in the control of lymphnodal disease (hyperfractionated = 55%, conventional = 57%; p = 0.92), but the disease control in the oropharynx only was significantly improved in the hyperfractionation arm (84% vs 64%, p = 0.02). Overall survival rate at 42 months was 27% for the hyperfractionation arm and 8% for the conventional (p = 0.03). Survival rates for hyperfractionated versus conventional RT were 40% versus 18% (p = 0.06), respectively, for Stage III patients and 16% versus 0% (p = 0.15), respectively, for Stage IV. There was significant improvement in survival in favor of the hyperfractionation arm in patients with lesions outside the base of the tongue (31% vs 15%, p = 0.02), for those with a 50-70% Karnofsky status (19% vs 0%, p = 0.006) and for patients with N0/N1 disease (38% vs 15%, p = 0.03). Acute toxicities were of similar magnitude, although both skin and mucosal reactions appeared earlier on the hyperfractionation scheme. To date, no differences in late toxicity have been observed. We conclude that in a subset group of patients with locally advanced carcinoma of the oropharynx, hyperfractionated radiotherapy appears to provide improved survival without adding to increased toxicity.