Two recent papers on reducing vessel collisions with large whales are available. Silber, G.K, A.S.M. Vanderlaan, A. Tejedor Arceredillo, L. Johnson, C.T. Taggart, M.W. Brown, S. Bettridge, and R. Sagarminaga. 2012. The role of the International Maritime Organization in reducing vessel threat to whales: process, options, action and effectiveness. Marine Policy is at: http://www.sciencedirect.com/science/article/pii/S0308597X12000528 (abstract below) and Silber, G.K. and S. Bettridge. 2012. An assessment of the Final Rule to implement vessel speed restrictions to reduce the threat of vessel collisions with North Atlantic right whales. NOAA Technical Memorandum NMFS-OPR-48. is available at: http://www.nmfs.noaa.gov/pr/pdfs/shipstrike/assessment_nmfsopr48.pdf Silber, G.K, A.S.M. Vanderlaan, A. Tejedor Arceredillo, L. Johnson, C.T. Taggart, M.W. Brown, S. Bettridge, and R. Sagarminaga. 2012. The role of the International Maritime Organization in reducing vessel threat to whales: process, options, action and effectiveness. Marine Policy Abstract Ocean-going vessels present a measurable threat of lethal collision with many marine species worldwide, notably large whale species of which many are endangered. Various modifications to conventional vessel operations have been recently used to reduce the threat. Some of the modifications have been instituted by coastal states as a result of their adoption by the International Maritime Organization (IMO) — a specialized agency of the United Nations that is the recognized authority for international maritime shipping interests and their safety of navigation at sea. We describe the processes through which coastal states can approach the IMO to seek review and adoption of environmental conservation proposals involving international shipping. We also provide a description of vessel navigation modifications in specific geographic areas where IMO-adopted measures to protect large whales have been implemented — there are only 10 such cases and we describe each. We then address the methods that can and have been used to assess the effectiveness of such measures. As weighed against the goals of the modifications by estimating the ensuing reduced risk to whales, actions taken are generally regarded as being successful in reducing the risk, but to varying degrees. We conclude that the IMO can be a powerful entity in providing solutions to a range of marine environmental and conservation problems. When used in concert with related efforts such as mariner education, the IMO, and the range of navigational measures available to it, is an effective forum through which coastal states can pursue large whale conservation objectives without unduly compromising the activities of shipping interests.