This paper examines the impact of supplementary web-based materials on students' academic performance in a first-year economics unit at university. In particular, the paper considers the impact of students' usage of the unit's webpage, voluntary on-line discussion board, voluntary on-line quizzes and voluntary on-line homework questions on their final mark in the first-year economics unit. It finds that students who make use of on-line materials perform better in the unit than students who do not, holding prior academic ability constant. The paper also finds that students' usage of on-line supplementary materials does not vary according to their academic ability.