Recent collision and grounding accidents have increased public and industry awareness of the risks of oil spills from bunker tanks. This paper summarizes historical spill data for freighters, and provides case histories for representative collision, allision, and grounding casualties. Arranging double-hull protection around the bunker tanks is one means for mitigating the risk of spillage. The location and size of the fuel oil tanks also influences the likelihood and expected volume of oil spills. The relative effectiveness of these alternatives are explored using probabilistic oil outflow analysis techniques collision of Alexia and Enit— Gult of Mexico, 1995