Environmental issues have added a new dimension to multilateral diplomacy and will be of growing importance. This superb book on the negotiations leading to the Montreal Protocol on Substances that Deplete the Ozone Layer, adopted in 1987 and revised in 1990, was written by the head of the U.S. delegation. It makes clear that governments will often have to act while there is still much scientific uncertainty, balancing the risks and costs of acting against those of not acting. Industry, scientists and the private sector will have even more important roles to play than in traditional diplomacy. This is an authoritative well-written work.