OBJECTIVES: I. Determine the maximum tolerated dose of fludarabine that can be given during the sixth and seventh weeks of radiotherapy in patients with locally advanced squamous cell carcinoma of the oral cavity, pharynx, or larynx, based on the systemic toxicity of the drug and the acute mucosal reactions in the irradiated fields. II. Document the qualitative and quantitative toxicity of this combination therapy in this patient population.