This study examined how Supplemental Instruction (SI) visits help traditionally disadvantaged students reduce the performance gap in their courses. A student is defined as holding a "disadvantaged" status when he or she can identify with the following factors: underrepresented minority status, first-generation status, Federal Pell Grant eligible status, and English/mathematics remedial status. This study revealed that students including both disadvantaged and nondisadvantaged would benefit from an increase of SI participation. The more disadvantaged students gained larger performance improvement than less disadvantaged students with more SI visits, indicating the importance of regular SI participation for disadvantaged students to close the performance gap with nondisadvantaged students.