There is no definitive approach to assessing the effectiveness of international environmental regimes. In order to explore the regime established by the 1979 Geneva Convention on Long-Range Transboundary Air Pollution this article broadly integrates the approach to effectiveness taken by Peter H. Sand in The Effectiveness of International Environmental Agreements, and Daniel Bodansky in The Art and Craft of International Environmental Law. The article finds that compliance, institutional, and normative effectiveness can be evaluated relatively confidently. An effectiveness assessment of the long-range transboundary air pollution (LRTAP) regime indicates that, on the whole, it has helped states to reach agreement on contentious issues and achieve results in air pollution reduction. However, it faces significant challenges with regard to participation, implementation procedures, empowerment of domestic stakeholders, and funding. The article provides an in-depth and up-to-date look at the LRTAP regime, including the most recent amendments and its relationship with European Union and international law.