Oral mucositis is a common side-effect associated with conventional cancer therapy and has also recently been reported in association with newly emerging cancer therapies. It is characterized as an inflammation of the oral mucous membranes accompanied by many complex mucosal and submucosal changes. Ulcerative oral mucositis can cause significant oral pain, impair nutritional intake, lead to local or systemic infection, and cause significant economic cost. In addition, it may necessitate interruptions in cancer therapy, thus adversely affecting patient prognosis. This review presents the current understanding of the pathogenesis of mucositis and discusses evidence-based clinical management strategies for oral mucositis. In addition, key research questions for future investigation are identified, followed by a discussion of strategies to promote development and funding of the needed research.