When oil spills occur in U.S. waters, federal law places primary liability on the vessel owner or operator -- that is, the responsible party -- up to a statutory limit. As a supplement to this "polluter pays" approach, a federal Oil Spill Liability Trust Fund administered by the Coast Guard pays for costs when a responsible party does not or cannot pay. This book is based on a GAO report on oil spill costs and select program updates on the recent San Francisco spill. Specifically, it answers three questions: (1) How many major spills (i.e., at least $1 million) have occurred since 1990, and what is their total cost? (2) What factors affect the cost of spills? and (3) What are the implications of major oil spills for the Oil Spill Liability Trust Fund?