The safe destruction and dismantling of chemical, nuclear and conventional weapons is of fundamental importance to the security of a number of countries represented in this volume. Expertise in the field is not confined to one country or organization: all can benefit from each other. There is an ever present danger of proliferation of weapons of mass destruction: approximately two dozen countries have ongoing programmes to develop or acquire such weapons, and many are also gaining the capability to build air-surface delivery systems. But much can be done to prevent proliferation by reducing leakage of materials and know-how and by solving the problems of the destruction of surplus weapons systems, which has now come to be a key issue.