Transmucosal Immediate-Release Fentanyl（TIRF）can be a key-drug for breakthrough cancer pain. Prescription audit is needed because there are concerns about tolerance or serious adverse events including respiratory suppression and addiction due to inappropriate use of these drugs. The aim of this audit study is to evaluate appropriateness of TIRF prescriptions, reasons of violation, and adverse events in the real-world setting. A retrospective chart review was conducted in 31 patients who had breakthrough cancer pain and were treated with TIRF. A 2-step algorithm was generated：baseline pain and administration situation of other opioid rescues. TIRF was prescribed appropriately in six patients（19.4％）. Reasons of violation were as follows：prescriptions only for using same drug with around-the-clock opioids（fentanyl transdermal patches, n＝19）, and patients could take oral medicines and use of morphine or oxycodone rescues would be preferable（n＝12）. TIRF was initiated with a minimum dose in all patients and no serious adverse events were observed. Although TIRF was used widely for breakthrough cancer pain, prescription was not necessarily done appropriately. Detailed assessment of breakthrough cancer pain and consideration of the use the other rescue medication would be required.