An early phase II clinical study of 254-S, a new anticancer platinum complex, for head and neck cancer was conducted by the 254-S Head and Neck Cancer Study Group consisting of 10 institutions. Based on the results obtained in the phase I study, 254-S was administered at 100 mg/m2 by 60 min intravenous drip infusion after being dissolved in 300 ml of 5% xylitol. In principle, the 254-S administration was repeated at least 2 times at 4 week intervals. Hydration was performed, if needed. All 24 cases registered were regarded as complete cases evaluable for tumor response. Complete response (CR) was observed in 4 patients (16.7%), partial response (PR) in 5 (20.8%), no change (NC) in 11 and progressive disease (PD) in 4, for a 37.5% response rate. Three CR and 3 PR (40.0%) were obtained in 15 patients with prior chemotherapy, including 1 CR and 2 PR (33.3%) in 9 patients previously treated with cisplatin. Side effects were observed in 19 patients (79.2%). Major toxic effects were hematotoxicity, including thrombocytopenia (58.3%), leukopenia (58.3%) and anemia (33.3%), and gastrointestinal toxicity, including nausea and vomiting (45.8%) and anorexia (37.5%). Abnormal parameter changes on renal function were found in 2 patients (8.3%). Based on these results, it was concluded that 254-S is potentially a useful anticancer agent for the treatment of head and neck cancer, and should be further investigated in a late phase II clinical study.