OBJECTIVE To determine the safety profile and activity of the combination of docetaxel, cisplatin and 5-fluorouracil (5-FU) in chemotherapy-naive patients with squamous cell carcinoma of the head and neck (SCCHN). METHODS Patients with locally advanced unresectable SCCHN were treated with docetaxel and cisplatin both as a 1-h infusion on day 1 followed by a continuous infusion of 5-FU for 5 days. Cycles were planned every 3 weeks up to four cycles, whereafter the patients were treated with locoregional radiotherapy. Two dose levels were studied. Doses in level I were 75 mg/m(2) of docetaxel, 75 mg/m(2) of cisplatin and 750 mg/m(2)/day of 5-FU; in level II the cisplatin dose was escalated to 100 mg/m(2). Following chemotherapy, all patients were to receive curative radiotherapy according to the standards in the different institutions. RESULTS Twenty-five patients were treated at dose level I with 86 cycles (median four; range one to four), and 23 at dose level II with 84 cycles (median four; range two to four). The median relative dose intensity was 0.99 (range 0.86-1.04) at level I and 0.94 (range 0.79-1.02) at level II. The response rate in the intention-to-treat population was 64% [95% confidence interval (CI) 42.5% to 82%] in level I and 78.3% (95% CI 56.3% to 92.5%) in level II; all were partial responses. The maximum tolerated dose was reached at level II with renal toxicity, nausea, stomatitis and thrombocytopenia as principal dose-limiting toxicities. The median survival of the 48 patients was 18.5 months. The survival at 12, 18, 24 and 30 months was 69, 54, 41 and 31%, respectively. CONCLUSIONS The combination of docetaxel, cisplatin and 5-FU associated with prophylactic ciprofloxacin is feasible and active in patients with SCCHN. Dose level I is recommended for phase III testing.