In this study, we used logistic regression to examine how well student background and prior achievement variables predicted success among students attending accelerated and enrichment mathematics courses at a summer program (N = 459). Socioeconomic status, grade point average (GPA), and mathematics diagnostic test scores significantly predicted achievement in accelerated courses, and age, ethnicity, and GPA significantly predicted achievement in enrichment courses. These findings may be useful in determining which students are more likely to do well in accelerated and enrichment mathematics courses at a summer program. (Contains 3 tables.)