Asynchronous online discussion is used in a variety of ways, both in online learning environments and in traditional teaching environments where, increasingly frequently, a blended approach is adopted. However the anticipated benefits of this tool in improving student learning outcomes are still being debated. One of the many factors affecting the outcomes of asynchronous online discussion is that of assessment. This study investigated the influence of assessment of discussion postings on the achievement of discussion outcomes as perceived by instructors. The findings indicate that the incorporation of assessment results in higher levels of discussion outcomes than if no assessment were used. The use of a subsequent assessment based on the online discussion was also examined, but the results were inconclusive. (Contains 6 tables and 1 figure.)