An oilspill risk analysis was conducted to determine the relative environmental hazards of developing oil in different regions of the Northern Gulf of Alaska Outer Continental Shelf lease area. The study analyzed the probability of spill occurrences, likely paths of the spilled oil, and locations of resources vulnerable to spilled oil. The combined results yielded estimates of the overall oilspill risks associated with development of the proposed lease area. The analysis implicitly includes estimates of weathering rates and slick dispersion and an indication of the possibility of mitigating effects by cleanup efforts. The leasing of the tracts proposed for Sale 55 will result in an expected number of 2.8 spills. The estimated probability that land will be contacted by one or more spills within 30 days is 0.84; however, this probability varies greatly for the different targets and different contact times.