EORTC protocol 22791 compared once daily fractionation (CF) of 70 Gy in 35-40 fractions in 7-8 weeks, to pure hyperfractionation (HF) of 80.5 Gy in 70 fractions in 7 weeks using 2 fractions of 1.15 Gy per day, in T2-T3 oropharyngeal carcinoma (excluding base of tongue), N0,N1 of less than 3 cm. From 1980 to 1987, 356 patients were entered. In the final analysis (June 1990), the local control was significantly higher (p = 0.02 log-rank) after HF compared with CF. At 5 years, 59% of patients are local disease-free in the HF arm compared to 40% in the CF arm. The superiority of HF was demonstrated in patients staged T3N0,T3N1 but not in T2. The Cox model confirmed that the treatment regimen was an independent significant prognostic factor for locoregional control (p = 0.007 log-rank). This improvement of locoregional control was responsible for a trend to an improved survival (p = 0.08 log-rank). There was no difference in late normal tissue damage between the two treatment modalities.