BACKGROUND: Oral mucositis (OM), one of the side-effects induced by chemotherapy, has 40% incidence and the incidence rate increases to approximately 100% in combination with radiotherapy. We describe OM in ICR mice induced using 5-fluorouracil (5-FU) and 20% acetic acid. MATERIALS AND METHODS: We optimized the dose of 5-FU and 20% acetic acid and validated the efficacy of standard therapies for OM. RESULTS: All mice developed OM after administration of 5-FU and 20% acetic acid. Application of Kenalog® reduced maximum ulcer area and the duration of spontaneous recovery in a dose-dependent manner. CONCLUSION: We succeeded in developing a mouse model of OM induced by cancer chemotherapy. New drugs for OM induced by anticancer drugs can be evaluated simply by monitoring the WBC count in this mouse model. This model is expected to contribute to development of new drugs and elucidation of the mechanisms of ameliorating stomatitis as a side-effect of anticancer drugs.