Effectiveness of a peer tutoring system developed for an advanced physiology course was assessed in terms of academic performance and perceived value. Forty-five students took the course without the peer tutoring system, and sixty-nine students took the course with peer tutoring. Grades from both groups of students were compared with grades earned in an introductory physiology course. Tutored students were asked how much they valued the peer tutoring. There was a decline in grades received by the students in the advanced physiology course compared with their scores in the introductory physiology course in both tutored and untutored groups. However, the decline in the tutored group was significantly (P = 0.015) less than that in the untutored group of students. Tutored students reacted very favorably to the tutoring sessions and expressed a desire to see tutoring expanded to other courses. This was the first demonstration of the effectiveness of peer tutoring in college science teaching. Peer tutoring appears to be effective in enhancing student performance as well as being perceived as beneficial by the students.