Many countries have the capacity to construct nuclear weapons - even relatively poor and small ones, as the North Korean example shows us. So far, only one country - South Africa – has voluntarily given up its nuclear weapons programme. Three others - Ukraine, Kazakhstan and Belarus - gave up the Soviet Union’s nuclear weapons after the end of the Cold War. A number of others (including Australia, Sweden and Switzerland) have at one time or another made plans to build nuclear weapons, but eventually opted not to do so. These stories can shed significant light on the prospects for nuclear disarmament – one of the biggest global challenges of our time. Yet they have received little scrutiny in the academic literature to date. This volume addresses that gap, bringing together scholars, practitioners and politicians to reflect on the history of nuclear exits (and nuclear non-entries) and to draw out some key lessons for future nuclear disarmament and non-proliferation efforts. Although progress on reducing nuclear arsenals has been frustratingly slow, there are strong indications that world opinion is increasingly supportive of nuclear exits. Organizations such as International Physicians for the Prevention of Nuclear War, the International Committee of the Red Cross and the World Medical Association have all taken a strong stand against nuclear weapons. Ultimately ridding the world of nuclear weapons requires politicians to take determined action – to decide in favour of nuclear exits. The chapters in this volume show that such decisions are possible and that a worldwide nuclear exit is achievable – within our lifetimes. This book was published as a special issue of Medicine, Conflict and Survival.