Purpose: Early defibrillation is essential for survival from ventricular fibrillation (VF). In Korea, assessment of clinical skills, including electrical defibrillation, has been part of the medical licensing examination since 2009. Although one defibrillator is used in the exam, various defibrillators are used in the real world. We wanted to know whether unfamiliar devices might affect defibrillation skill. Methods: Our research was performed during conduct of the objective structured clinical examination (OSCE) for sixth grade medical students. Three different defibrillators were used for the test; CodeMaster, LiFEGAIN, and HEARTSTART MRx. CodeMaster was the defibrillator used for education and training. In the test room, VF was simulated by use of a simulator (SimMan?), and one of the three defibrillators was placed randomly. A checklist, where eight items among a total of 13 items were for device operation, was used for assessment of defibrillation skill. The written exam and clinical practice score for emergency medicine and defibrillation skill score were investigated. In addition, each operation time of device (turn-on, charge, and shock) was calculated with review of video resources containing the entire exam process. Results: Among 65 students enrolled, 59 students were included for analysis. Students were divided according to CodeMaster (n=20), LiFEGAIN (n=15), and HEARTSTART MRx (n=24). No significant difference in the score on the written exam and clinical practice was observed among the groups. In addition, the scores for defibrillation skill and the time intervals did not differ among the groups. Conclusion: Unfamiliar devices may not affect defibrillation skill in medical students.