Chemotherapy-induced oral mucositis is a common adverse event in breast cancer patients. Breakdown of the mucosal barrier predisposes the patient to bacterial, fungal and viral superinfection, especially candidiasis. We demonstrated the frequency of chemotherapy-induced oral mucositis and oral candidiasis, and the efficacy of antimycotic agents in breast cancer patients. We investigated 32 patients with advanced and metastatic breast cancer who underwent chemotherapy in our department from March, 2009 to August, 2010. The chemotherapy regimens were as follows: FEC (epirubicin/5-FU/cyclophosphamide) followed by taxanes: 21, FEC: 1, TC (docetaxel/cyclophosphamide): 7, DOC (docetaxel): 3, and CPT-11/S-1: 1. Patients had blood and bacteria tests of the oral cavity at the time mucositis symptoms appeared. We administered an antimycotic agent (itraconazole) and evaluated its effect on mucositis at the time mucositis symptoms appeared. 56. 3% of patients had chemotherapy-induced oral mucositis, and 38. 9% of the mucositis patients had oral candidiasis. The incidence of mucositis increased when severe neutropenia occurred. 92. 9% of mucositis patients were cured or improved by itraconazole. In conclusion, chemotherapy caused oral candidiasis in 40% of cases with oral mucositis, and in about 56% of breast cancer patients. The antimycotic agent may be useful for chemotherapy-induced oral mucositis in breast cancer patients.