A cooperative phase II study of cisplatin in head and neck cancer was conducted in 23 institutions. Eighty-nine patients were entered into this trial, of which 73 were evaluable. Two different regimens were employed in this study. Regimen A: cisplatin 10 mg/m2 intravenous (i.v.) infusion daily, days 1-5, q 3 wk. Regimen B: cisplatin 50 mg/m2 i.v. infusion, day 1, q 3 wk. Two patients achieved complete response and 17 achieved partial response with an overall response rate of 26.0%. By histological types, the response rate was 26.3% in the case of squamous cell carcinoma. Partial response were observed in 2 cases of adenocarcinoma and in one case each of adenoid cystic carcinoma and transitional cell carcinoma. The response rate was 19.4% for previously treated patients, as compared to 63.6% for the previously untreated group. Toxic effects were observed in 94.7% of 76 evaluable cases. From 50 to 68% of patients experienced nausea, vomiting and anorexia. No patient exhibited a serum creatinine level exceeding 2 mg/dl. Anemia and leukopenia were observed in 58.9% and 32.9% respectively. It is therefore concluded that cisplatin is markedly useful for the treatment of head and neck cancer.