Purpose/Objective: Acute mucositis is a serious dose-limiting side effect during and immediately after primary RT, concurrent chemoradiation (ChemoRT) or a combination of cetuximab and accelerated RT (bioradiation or BioRT) resulting in compromised oral intake due to pain and dysphagia. The purpose of this study was to identify pre treatment variables and DVH parameters that might predict acute mucositis grade 2-4 at the end of the treatment. Conclusions: The severity of acute mucositis in the last week of primary RT, ChemoRT or BioRT in head and neck cancer patients can be predicted by two pre treatment variables and one DVH parameter (V60). The use of V60 can be helpful in IMRT optimization to reduce this side effect or select high-risk patients for intensified supportive care.