The late 1980s and early 1990s were a period of increased interest in reducing transit bus emissions and exploring alternatives to traditional diesel-powered transit buses. As a result, the first U.S. fuel cell bus (FCB) demonstration programs were implemented. These early efforts focused on proving the concept of fuel cells to power transit buses. This book reviews past and present fuel cell bus technology development and implementation, specifically focusing on experiences and progress in the United States. The primary focus is on descriptive comparisons of fuel cell transit bus operation in the U.S. and on the industry's need to continue successful implementations of these advanced technologies.