[en] Purpose: To quantify the incidence and severity of acute local toxicity in head and neck cancer patients treated with radiotherapy (RT), with or without chemotherapy (CHT), using the Common Terminology Criteria for Adverse Events, version 3.0 (CTCAE v3.0), scoring system. Methods and Materials: Between 2004 and 2006, 149 patients with head and neck cancer treated with RT at our center were prospectively evaluated for local toxicity during treatment. On a weekly basis, patients were monitored and eight toxicity items were recorded according to the CTCAE v3.0 scoring system. Of the 149 patients, 48 (32%) were treated with RT alone (conventional fractionation), 82 (55%) with concomitant CHT and conventional fractionation RT, and 20 (13%) with accelerated-fractionation RT and CHT. Results: Severe (Grade 3-4) adverse events were recorded in 28% (mucositis), 33% (dysphagia), 40% (pain), and 12% (skin) of patients. Multivariate analysis showed CHT to be the most relevant factor independently predicting for worse toxicity (mucositis, dysphagia, weight loss, salivary changes). In contrast, previous surgery, RT acceleration and older age, female gender, and younger age, respectively, predicted for a worse outcome of mucositis, weight loss, pain, and dermatitis. The T-score method confirmed that conventional RT alone is in the 'low-burden' class (T-score = 0.6) and suggests that concurrent CHT and conventional fractionation RT is in the 'high-burden' class (T-score = 1.15). Combined CHT and accelerated-fractionation RT had the highest T-score at 1.9. Conclusions: The CTCAE v3.0 proved to be a reliable tool to quantify acute toxicity in head and neck cancer patients treated with various treatment intensities. The effect of CHT and RT acceleration on the acute toxicity burden was clinically relevant