For more than 40 years, nuclear weapons scientists and arms control advocates have sought an international agreement that would end the development and testing of nuclear weapons. The culmination of that effort, the Comprehensive Test Ban Treaty, was signed by 152 nations in 1996. The treaty is of particular benefit to the United States, which did more than any other nation to formulate its language and which holds a lead in both nuclear weapons design and the computer-simulation technology that will be used to study weapons in the absence of testing.

The US Senate, which must ratify the treaty with a two-thirds majority if it is to take effect, is debating its contents this week and may vote next Tuesday on its ratification (see page 519). During hearings before the vote, the scientific and military leadership of the United States will testify in favour of the treaty. Treaty critics claim that the US nuclear weapons laboratories' stockpile stewardship programme cannot assure the safety and reliability of the nuclear weapons stockpile in the absence of testing. But the laboratory directors, as well as independent technical advisers to the US government, believe that stockpile stewardship will work. Thirty-two US Nobel laureates in physics will this week release a letter expressing the same view.

The critics also contend that verification of compliance with the treaty will be impossible, as seismologists will be unable to identify small underground nuclear tests. The Central Intelligence Agency has just released an assessment stating that it will be unable to detect small, sub-critical explosions under the treaty regime. But sub-critical tests are permitted by the treaty. The American Geophysical Union and the Seismological Society of America will restate this week that the monitoring system to be established under the treaty is sufficient to meet its verification goals.

If the treaty is considered by the Senate on its merits, it should obtain the 67 votes needed for ratification by the United States—rapidly leading to a similar outcome in most, if not all, of the 44 nations that must ratify it before it takes effect. Alas, the timing and circumstances of the vote put pressure on Republican senators to oppose the treaty on partisan grounds. Some Democrats, much to their discredit, are banking on this so that they can portray the Republicans as proponents of nuclear war during next year's elections. Republican senators such as Richard Lugar (Indiana) and Pete Domenici (New Mexico) must confound them by rising above partisan considerations on Tuesday and voting to ratify the treaty.