This case study explains how an ecosystem recovers from a major one-time insult such as an oil spill. It begins with an account of the grounding and rupture of the Exxon Valdez, the ship that caused the spill. The amount of oil remaining in the ecosystem and the remaining impact of the spill are covered next. Then transition of the ecosystem is described as it gradually recovers. The next section declares that biologists consider the intertidal communities in Prince William Sound to be still recovering, but not completely recovered. Another section gives students a chance to view real time data and periodic photographs of a large boulder (Dr. Mearns' Rock) in the affected area. Other features include an oil spill trajectory model, an oil spill primer for students, an explanation of the toxicity of oil, an ask-an-expert feature, and information about how to report a spill.