The use of PowerPoint slides has become an almost ubiquitous practice in university classrooms, however little research has examined whether the timing of lecture slide availability to students (either before or after lecture) affects classroom behaviour or exam performance. Using a 2 (slide availability condition) x 2 (course type) between-subjects design, the present study examined lecture slide availability differences in attendance, participation, and exam performance in two courses--Research Methods and Cognitive Development--taught in both the Fall and Winter semesters. For each type of course, lecture slides were made available on the course website before lecture in one semester and after lecture in the other semester. Course material was held constant across semesters. Results showed that mean attendance was higher when slides were available before lecture, but only for the type of course that did not include attendance points as part of students' final grades. For students who participated in class, participation was more frequent when slides were available before lecture. No significant difference in exam performance was found between lecture slide availability conditions, however. These findings suggest that making lecture slides available to students before lecture may lead to better overall attendance and participation, but exam performance is determined by more than just whether or not students have lecture slides available for their note-taking. (Contains 3 tables and 4 figures.)