This book examines the prospects and challenges of a global phase-out of highly enriched uranium and the risks of this material being used by terrorists to make a bomb. Terrorist groups, such as Al Qaeda, have demonstrated repeatedly that they seek to acquire nuclear weapons. This volume explains how the simplest path to a terrorist bomb could be blocked without hindering scientific progress, medical care, or national security. Unknown even to many security specialists, tons of bomb-grade uranium are trafficked legally each year for ostensibly peaceful purposes, raising grave risks that terrorists or rogue states will divert some of it for nuclear weapons. If terrorists obtained even a tiny fraction of this bomb-grade uranium less than 100 pounds they could potentially construct a nuclear weapon with a yield like the Hiroshima bomb, equivalent to millions of pounds of conventional explosives. Nuclear experts and policymakers have long known of this danger but so far have taken only marginal steps to address it. This volume starts by highlighting the lessons of past successes where bomb-grade uranium commerce has been eliminated such as from Argentina's manufacture of medical isotopes. Next, it explores some hopeful progress, including Washington's steps to eliminate HEU from all U.S. nuclear research reactors by 2020. But the heart of the book confronts the major challenges that still lie ahead. For example, Russia resists eliminating HEU from any of its reactors, and the U.S. Navy uses more bomb-grade uranium than the rest of the world combined. Each of the book's thirteen case studies offers advice for reducing HEU in a specific sector. These insights are then distilled into eight concrete policy recommendations for U.S. and world leaders to promote a global phase-out of bomb-grade uranium. This book will be of much interest to students of nuclear proliferation, global governance, international relations and security studies.