Supplemental Instruction (SI) is a program that seeks to improve student success by targeting classes with high failure rates, as defined with a failure percentage of 30% or more. It is organized by an administrative SI supervisor who supervises SI leaders, which are students that have successfully completed the courses that they have been assigned. The SI supervisor also collaborates with the course instructors who aid in screening the competency of the SI leaders. Improved self-confidence, teamwork, independence and course performance have been reported as benefits of SI. This project sought to explore the effect of SI on success and failure, along with gender, age and race. The type of course was also used as a factor in order to control for it as a confounding variable. In order to ascertain the effect of these variables on success, a technique called logistic regression was used. Caucasian female students who took bacteriology and did not attend SI were used as the reference group. Students were about twice as likely to succeed if they completed the required number of SI sessions and one fifth as likely to succeed if they were in a SI class and did not meet the minimum number of sessions. Hispanic students were 40% as likely to succeed, and African American students were about one third as likely to succeed when compared to Caucasian students. Students between 20 and 29 years old were half as likely to succeed, and those 30 or older were one quarter as likely to succeed when compared to teen students. Those in algebra were about three times more likely to succeed than those in bacteriology, chemistry and statistics. When the students that withdrew were removed, the chances of success were about the same, except for African American students which were one quarter as likely to succeed, and those that did not meet minimum sessions were one quarter as likely to succeed. The model explained more variation when the students that withdrew were included. As SI had a strong influence on success, it should be considered as a tool to enable retention of students in high risk courses.