At the Non-proliferation Review Conference in 1990, several states, parties to the NPT, intimated that they would oppose any lengthy extension to the Treaty if the issue of nuclear testing remained unresolved. While the increase in radioactive fallout was now considerably less than hitherto, the spread of nuclear weaponry, or the spread of its potential, was clearly discernible. States such as North Korea and Iraq were certainly seen as contenders for a place in the nuclear circle. Research and development were going ahead whether in the laboratory or out on the proving grounds. Nuclear testing must be checked. In 1990, 27 years had elapsed since a partial test ban treaty. Testing in the atmosphere, in outerspace, under the sea, had all been prohibited under the terms of the 1963 Treaty but not testing underground. Half a century of talking had not brought any definitive end to nuclear testing and the likelihood of proliferation. How had this state of affairs come about? What had delayed decision? Who had been participants in the disputation-at the UN and elsewhere? And was the UN the forum best suited to the resolution of the problem of testing? In 1995, these questions still need answering.