An open-label, non-randomized study evaluated the feasibility and efficacy of filgrastim (recombinant methionyl human granulocyte colony-stimulating factor, r-metHuG-CSF) to prevent mucositis induced by accelerated hyperfractionated radiotherapy (1.6 Gy b.i.d., total dose 67.2 Gy in six weeks with a two-week split) and concomitant chemotherapy (cisplatin, 20 mg/m2/day, days 1-5 by continuous intravenous infusion) in patients with laryngeal carcinoma. Filgrastim 300 microg/day was administered on days 1, 3, and 5 in weeks 2-6 of radiotherapy, after the second fraction. Twenty patients (three stage II, six stage III, and eleven stage IV, according to AJCC) were enrolled in the trial. Oral mucosal toxicity was grade 2 in nine patients (45%), grade 3 in eight (40%), and grade 4 in three (15%). Severe hematological toxicity (WHO criteria) was uncommon. Nineteen patients (95%) completed the treatment in the planned time. Overall survival was 55% at three years. The administration of filgrastim with this regimen was feasible, and it appeared to reduce the severity and duration of mucositis induced by the combined treatment.