Thirteen patients with advanced head and neck cancer were entered into a phase II study of fludarabine phosphate. Fludarabine phosphate was given by continuous infusion for 5 days, at a starting dose of 20 mg/m2 per day for patients previously treated with one regimen and 25 mg/m2 per day for previously untreated patients; therapy was repeated every 3-4 weeks. Of the 13 patients, 3 had undergone one prior regimen and 10 patients were previously untreated by chemotherapy. No responses were observed. Myelosuppression was the most common toxicity observed. Four patients developed mild nausea, vomiting and seven developed bleeding stomatitis that resolved in one week. In addition, four patients developed headaches which resolved spontaneously. No renal, hepatic, or neurotoxicity was observed. Our study demonstrates that in previously treated and untreated patients, fludarabine phosphate given on this schedule has little activity in patients with advanced head and neck cancer.