This report, the fifth publication from OTA's assessment on the proliferation of weapons of mass destruction, examines the whole range of consequences for proliferation of the Soviet Union's breakup. One effect may be the erosion of international nonproliferation treaty regimes. In spite of the continuing desire of most of the newly independent states of the former Soviet Union to support nonproliferation goals, these states face severe internal challenges; social and economic disruption are rampant and the degree of central governmental control over activities nominally within their jurisdictions is often questionable. Of particular concern are economic hardship and low morale among many individuals with access to vital weapon information or sensitive facilities, a situation aggravated by as yet inadequate national systems to account for and secure nuclear materials, to control exports, and to police borders. Given the severity of the problems facing Russia and the other newly independent states, the United States and other Western powers may have only marginal ability to influence the overall course of events there. This study describes how U.S. assistance may reduce specific proliferation risks in the former Soviet Union. The consequences of failure to stem these risks provide a strong incentive for the United States to help the newly independent states address them.