Many teachers require their students to take cumulative exams, but there are surprisingly few studies that examine the benefits of such exams. The purpose of this study was to determine whether introductory psychology students who take cumulative exams throughout the semester would have better long-term retention than students who take a cumulative final exam after a series of unit (i.e., noncumulative) exams. As expected, the students who took cumulative exams throughout the semester did better on the cumulative portion of the final exam. This main effect evolved into an interaction on a follow-up test administered 2 months after the course ended. The long-term retention of good students was unaffected by the type of exams they took. However, low-scoring students remembered more of the course material when they took cumulative exams throughout the semester. (Contains 3 notes and 1 figure.)