This paper outlines the organization and operational scheme of medical course evaluation in National Taiwan University College of Medicine (NTUMC). The results of evaluation on teaching effectiveness of instructors are reported. Questionnaires were distributed to students of large-sized classes. The teaching effectiveness of each instructor was evaluated in terms of four dimensions: teaching attitude, course content, teaching methods and student's global assessment of the instructor. The evaluation was measured on a five-point Likert scale ranging from highly satisfied to extremely dissatisfied. A summary of student feedback was distributed to each instructor, the course coordinator and the department head. The total questionnaire return rate for the 1994 academic year was 65.5%. However, invalid responses counted for 21.9 ±0.2% of the four dimensions. As the questionnaires were mainly distributed by students in 1995 and 1996, the return rates dropped to 31.8% and 30.7%, respectively. The average number of instructors evaluated in each survey was (9.3 ± 2.0) for the academic years of 1994-1996. This might have accounted for the low response rate of the surveys. Summary statistics of 27,963 evaluations for 1995 revealed that students, in general, were satisfied with the 42 courses evaluated. With regards to the evaluation criteria of teaching attitude, course content, teaching methods, and student's global assessment of the instructor, students expressed a high rate of satisfaction: 46.3%, 33.1%, 35.0% and 32.0%, respectively. The rate of satisfaction with the four evaluation dimensions were 40.7%, 45.5%, 44.9% and 48.2%, respectively. Similar results were observed for the 1996 academic year. Statistical analysis showed that course content had the highest correlation with students' global assessment of the instructor amongst the three dimensions.