An oilspill risk analysis was conducted to determine the relative environmental hazards of developing oil in different regions of the Central and Northern California Outer Continental Shelf (OCS) lease area. The study analyzed the probability of spill occurrences, likely paths of oil slicks, and locations of resources vulnerable to spilled oil. The analysis included estimates of the time between spill occurrence and contact with resources. The combined results yielded estimates of the overall risks associated with development of the proposed lease area. Assuming that oil will be found in all parts of the lease area, and depending upon the routes chosen to transport oil from OCS platforms to the shore, the leasing of the tracts proposed for OCS Sale 53 will, depending upon how oil is transported to shore, result in an expected 2.0 to 3.1 spills. The estimated probability that land will be contacted by one or more oilspills which have been at sea less than 30 days is between 0.49 and 0.86.