Objective: The purpose of this study was to determine the efficacy of concurrent chemoradiotherapy using conventional radiotherapy combined with low-dose daily 5-fluorouracil (5FU) and cisplatin (CDDP) for the locally unresectable head and neck cancer patients. Patients and Methods: From September 1996 through December 2000, we carried out a phase II study of concurrent chemoradiotherapy with low-dose CDDP plus 5FU for the treatment of patients with unresectable squamous cell carcinoma of the head and neck. Chemoradiotherapy consisted of irradiation with 1.6–2.0 Gy/day for 5 days per week up to a total dose 68 Gy and CDDP 3 mg/m2 by intravenous infusion over 1 h plus 5FU 150 mg/m2 by intravenous infusion over 24 h per day for 5 days per week. Results: Ninety percent of the patients had stage IV disease, including 65% of patients with T4 disease. Thirty-three patients (83%) received the full treatment as planned; 39 (98%) received full-dose radiotherapy and 33 (83%) full-dose chemotherapy. Of the 40 patients evaluable for response, 20 (50%) achieved complete response (CR) and 12 (30%) partial response with an overall response rate of 80%. Among the 20 CR patients, 15 underwent endoscopic blind biopsies and 4 had positive lesions. The most frequently observed toxicity was mucositis. Ten patients developed grade III mucositis, and 3 patients required enteral nutritional support through a feeding tube. Grade III leukopenia, anemia and thrombocytopenia were observed in 28, 25 and 20% of the patients, respectively. The median duration of follow-up at the time of analysis was 18 months. The median survival time was 23 months. The responders survived longer (34 months) than the nonresponders (4 months; p < 0.05). Conclusion: This regimen is safe and efficacious in the treatment of patients with advanced unresectable head and neck cancer.