Irradiation mucositis is defined as an inflammatory-like process of the oropharyngeal mucosa following therapeutic irradiation of patients who have head and neck cancer. Clinically, it is a serious side effect because severe mucositis can cause generalized problems (weight loss, nasogastric tube feedings) and interferes with the well-being of the patient seriously. Grading mucositis is important for the evaluation of preventive and therapeutic measures. The object of this study was to develop a scoring method based on local mucositis signs only. Four clinical local signs of mucositis were used in this score: white discoloration, erythema, pseudomembranes and ulceration. Mucositis of the oral cavity was calculated during conventional irradiation protocol for 8 distinguishable areas using the 4 signs and their extent. A prospective evaluation of this method in 15 irradiated head and neck cancer patients displayed an S-curve reflecting a symptomless first irradiation week, followed by a rapid and steady increase of white discoloration, erythema and pseudomembranes during the second and third week. Oral candidiasis, generalized symptoms such as weight loss and the highest mucositis scores were seen after 3 weeks irradiation. The novel mucositis scoring method may be of value in studying the effect of hygiene programs, topical application of disinfectants or antibiotics on oral mucositis.