Thirty-five patients with head and neck carcinoma who were treated with a second course of radiotherapy for relapse or second malignancy at the Gustave Roussy Institute between 1973 and 1981 were studied. Immediate tolerance for total doses greater than 80 Gy was good but 37% of patients suffered from delayed necrosis or bleeding. Thirty-seven per cent of lesions were locally controlled at 3 months and 97% of patients showed a subjective improvement to reirradiation. Local control was obtained in 53% of patients aged between 40 and 60 as compared to 19% in other age groups, and was obtained in 55% of patients who were irradiated a second time with a dose greater than 60 Gy as compared to 8% for doses less than 60 Gy. Complications following treatment are related to failure to achieve local control and area of second treatment fields greater than 70 cm2. Survival was worse for those patients having an interval less than 12 months between the two courses of irradiation and those in whom local control was not achieved.