Research on the influence of class size on student academic achievement is important for university instructors, administrators, and students. The article examines the influence of class size--a small section versus a large section--in introductory political science courses on student grades in two comparable semesters. It is expected that students in the small-class section will perform significantly better on exams than students in the large-class section. The empirical analyses demonstrate, however, that class size does not significantly influence grades. Instead, prior political science knowledge, ACT scores, and course attendance significantly and positively influence student exam grades as well as final course grades.