To provide a handy reference for those concerned with ways to avoid the further spread, or proliferation, of nuclear weapons, the House Committee on Foreign Affairs and the Senate Committee on Governmental Affairs have since 1977 sponsored periodic publication of the Nuclear Proliferation Factbook. This fourth edition of the factbook includes a wide selection of basic documents and national and international statistical data pertinent to the proliferation of nuclear weapons. Following an introduction, major sections focus on: (1) basic documents (selected documents which provide basic information on the foundation of the international nonproliferation regime and on the legislative and executive branch components of U.S. policy); (2) nuclear weapons; (3) routes to nuclear weapons; (4) the nuclear fuel cycle; (5) nuclear reactors; (6) uranium supply and demand; (7) fuel reprocessing and spent fuel management; (8) nuclear exports and assistance; (9) nuclear industrial bases in nonweapon states; (10) safeguards; and (11) the non-proliferation treaty review conferences. (JN)