Editors' Summary: A federal district court in Colorado recently added fuel to the fires of state-federal conflicts by ruling that federal reserved water rights apply to wilderness areas. The reserved rights doctrine, the focus of controversy ever since it was first recognized by the Supreme Court in 1908, is disliked by many western water users since water is a limiting factor in continued western urban and industrial development and water appropriated for federal interests means less is available for state and private interests. This Comment discusses the ruling in Sierra Club v. Block and analyzes the potential for adverse impacts on existing water rights and the practical implications for wilderness.