Sixty-five patients were included in a randomized clinical study to evaluate the efficacy of local hyperthermia as a concomitant agent to radiotherapy in the treatment of carcinoma of the head and neck region. Local hyperthermia at 42-43 degrees C was generated by a 27 x 12 MHz radiofrequency diathermy unit and was used before radiotherapy in 33 patients; the remaining 32 patients were subjected to radiotherapy alone. The response in patients with early lesions (Stage I and II) was similar for both the groups, while in patients with advanced disease (Stage III and IV) a significantly better tumour control was obtained by the use of the combined treatment.