Background. The prognosis is poor in recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC). Triple combination therapy may increase tumor response. Methods. This phase I/II prospective trial first determined the dose-limiting toxicity and recommended dose of irinotecan with cisplatin and tegafur/uracil (UFUR) in phase I. Irinotecan was supplied at doses of 40, 50, 60, and 70 mg/m2 by using a standard 313 design. Doses of cisplatin and UFUR were held stable. In phase II, the recommended dose of irinotecan was administered intravenously (i.v.) over 90 min on day 1, with cisplatin 50mg/m2 i.v. over 60 min also on day 1, and oral UFUR 200 mg twice a day for 5 days every 2 weeks a cycle. Results. In the phase I portion, 14 patients were enrolled, and the dose level of irinotecan at 60 mg/m2 was defined as the recommended dose for the phase II portion of the study. Among 43 patients enrolled in the phase II portion, complete response was seen in 2 patients (4.7%) and partial response in 10 patients (23.3%), and the disease control rate was 39.5%. In a subgroup analysis of patients whose prior chemoradio therapy was more than 6 months earlier, a response rate of 40.7% and disease control rate of 59.3% were observed. Conclusion. Cisplatin/UFUR/irinotecan triple combination therapy is tolerated and effective for selected patients. Individualized choice of treatment will influence prognosis and quality of life in R/M HNSCC patients.