Purpose: This paper aims at reporting and examining the experiences of medical ethics education with case-based learning and large-group discussion. Methods: The subjects were a group of 100 students in the third year medical student. The medical ethics course was designed to minimize unidirectional lectures and to maximize interactive work with a large group at the classroom utilizing cases as teaching material. In the middle of the course, all students were divided into small group of 4～5 members. Each group was to find and, based upon group discussion, analyze each different case containing ethical dilemma, and present it as a midterm report. To examine the effectiveness of case based learning in medical ethics education in a large classroom, the authors analyze the students feedback and evaluation delivered in survey questionnaires from 94 out of 96 students. Results: Students feedback showed that small-group discussion, interactive work in a classroom, and case-based studies were effective as well as practicable for medical ethics education for a large group.