Oral mucositis is the inflammation that takes place in the oral epithelium, as a result of antineoplastic treatments such as radiotherapy, chemotherapy or bone marrow transplant, being very frequent in these treatments for oncohematologic disease. The consequences of this inflammation, not only affect the quality of life of the patient, but can also suppose a limitation in the application of the treatment, as well as an increase in the hospital stay and therapeutic costs. A main obstacle for the study of the mucositis, has been the lack of a system adapted for its valuation by means of the oral examination. Methods developed to measure and quantify the changes produced in oral epithelium as a result of treatment of cancer can be very varied from more simple methods, such as general scales with four or five degrees of severity that link the mucositis to the state of oral health, to specific scales of treatment. In this last type of scale the type of antineoplastic treatment that gave rise to the mucositis is identified giving a global severity score for the mucositis. The establishment of a common scale for the evaluation of mucositis is important, not only for clinical purposes but also for the investigation of the degree of toxicity of the different therapeutic regimes that give rise to the mucositis.