Nuclear explosions are the most visible manifestation of the arms race, and the conclusion of a multilateral treaty that will meaningfully restrict nuclear testing has for three decades been a priority. While some see testing as essential for the development of nuclear weapons and forupholding nuclear deterrence postures, others are acutely concerned about the possible health hazards of nuclear tests. Proponents of a comprehensive test ban, or a very-low-threshold test ban, are convinced that further test limitations are the first, indispensable steps that must be taken to haltand reverse the nuclear rivalry among the great powers and to prevent the spread of nuclear wapons to more countries. The Stockholm International Peace Researach Institute (SIPRI) and the Canadian Institute for International Peace and Security (CIIPS) have jointly conducted a thorough study of thecomplex technical and political issues involved in a possible cessation or limitation of nuclear tests. This SIPRI-CIIPS publication contains papers by leading physicists, nuclear weapon designers, seismologists, international lawyers, strategic analysts, political scientists, and former governmentadvisers and arms control negotiators. The editors' concise summary of all the issues and viewpoints is presented in the first part of the book, which also contains their own conclusions about the feasibility of achieving a meaningful test limitation that is adequately verifiable by existing orproposed technical means.