The study investigated the toxicity and efficiency of the concomitant administration of radiotherapy and carboplatin to patients with head and neck carcinomas. Sixty-three patients with head and neck squamous cell carcinomas, other than nasopharyngeal cancer and Stage I (UICC) laryngeal cancers, were treated by external radiotherapy and four courses of carboplatin at a dose of 100 mg/m2 per week. In two patients, only three courses were possible due to renal toxicity. In the other 61 patients, toxicities were self-limiting and no patient required interruption of carboplatin administration. No patient required discontinuation of radiotherapy because of acute toxicity. Of 61 evaluable patients, a complete response (CR) was obtained in 11.5% and a partial response (PR) in 60.7% at 40 Gy. In 41 patients treated to 65 Gy (including two patients with maxillary sinus carcinoma, who were treated by debulking surgery), CR was obtained in 76.9% and CR+PR was 100% at the end of treatment. The actuarial survival rate of the 63 patients at 2 years was 69.2%, with a median follow-up period of 24.4 months. One of 12 patients who received salvage surgery after radical radiotherapy has died due to poor wound healing after the surgery. The schedule was safe, providing a weekly check of serum samples was possible. It is likely that the rate of local control and vocal cord preservation in laryngeal tumours might improve if concurrent carboplatin is used. Careful follow-up is required to determine the long-term effect of concomitant carboplatin administration.