This study analyzed the effect of mathematics courses on a cohort of students at a 4-year university in order to compare the effect of mathematics on adult students, those 25 and older, and traditional-age students. The transcripts of the 118 adult students and the 3,747 traditional-age students who were freshmen in the fall of 1999 were compared. The main findings of this study were (1) the adult cohort was less academically prepared upon entering college and had lower graduations rates than traditional-age students, (2) adult students who matriculated academically prepared for college-level mathematics had similar graduation rates as younger students with similar mathematics preparation, and (3) adult students who were unprepared for college mathematics had significantly lower graduation rates than traditional-age students beginning their college mathematics at the same level. While the adult group in this study included a larger percentage of minority and part-time students, which may have contributed to the differences between the two groups, this study illustrates the pivotal role that mathematics plays in the success of adult students.