For the first time in nearly a century, alternative fuels are successfully competing with oil as a transportation fuel, and radically new electric propulsion designs are challenging the conventional internal combustion engine, To maintain and enhance the quality of life offered by modem automotive technology, while reducing oil use, requires the gradual transition to sustainable energy resources. Recent events in the development of advanced automotive technologies suggest that a transportation system based on hydrogen may offer the most viable method to power automobiles efficiently, sustainably, and without polluting the environment. Based on eight years of research, INFORM Inc., a New York City-based environmental research and education organization, in November 1995 published Harnessing Hydrogen: The Key to Sustainable Transportation, a book that presents a case for development of sustainable transportation technologies based on hydrogen fuel. It explains how solar energy resources can be tapped, transformed into hydrogen, and used pollution free to power automobiles. The book also investigates the synergy between natural gas, a common fuel in today's energy world, and hydrogen, a fuel of the future, and examines the pivotal roles both fuels can play in transportation over the decades ahead. INFORM's goal is to show how the vision of a sustainable transportation energy future based on hydrogen can be achieved through a logical progression of clearly defined steps, starting today. This paper provides an overview of the book's major topics, with a focus on pathways during the transition from oil-based automotive fuels to hydrogen.