Students in an introductory biology course who were given open-book exams during the semester earned significantly higher grades on these exams, but significantly lower grades on the closed-book final exam, than students who took in-class, closed-book exams throughout the semester. Exam format was also associated with changes in academic behavior; students who had upcoming open-book exams attended fewer lectures and help sessions and submitted fewer extra-credit assignments than students who had upcoming closed-book exams. These results suggest that open-book exams diminish long-term learning and promote academic behaviors that typify lower levels of academic achievement. (Contains 3 tables.)