The Exxon Valdez oil spill in 1989 was responsible for substantial seabird mortality in the Gulf of Alaska. The Barren Islands, with the largest seabird colonies in the path of the spill, were particularly hard hit. Because of insufficient prespill data, it is impossible to quantify the effect of the spill on murre populations. However, the large number of murres killed and the rapid increase in murre attendance following the spill showed that the spill did impact the population. The authors hypothesize that large numbers of nonbreeders or inexperienced murres replaced breeding murres killed by the spill. Post spill data showed lower murre reproductive success in 1990 than in 1991, which is consistent with the authors' hypothesis. In 1991, fledging success was over 0.8 fledglings/chick and continued to be high in 1993 and 1994, suggesting spill impacts were short lived. Significant numerical differences exist between the authors' data and those collected by U.S. Fish and Wildlife Service (USFWS) personnel. The low attendance numbers and poor reproduction they reported have been used to justify claims of extensive, potentially irreparable injury to murre populations. Data collection methods are at least partially responsible for causing USFWS to underestimate post spill murre populations and reproduction. Based on their data, the authors conclude that, although murres rafting near the Barren Islands suffered substantial mortality as a result of the Exxon Valdez oil spill, claims that the spill dramatically reduced colony attendance or reproduction of the remaining birds is not scientifically supportable.