While the Cold War has ended and the threat of nuclear exchange between the great powers seems to have diminished a little, a number of developing countries have acquired or are working to obtain atomic weapons and other weapons of mass destruction. One recently rumoured development is ‘gamma-ray weapons’. These are nuclear isomer weapons, which might be based on hafnium-178, allowing a warhead of only a few grams to yield the equivalent of 100 kg of high explosive, plus a lethal burst of radiation. If the rumours prove correct, and the weapons are easier to acquire than atomic bombs, the world will become more insecure than ever before. Terrorism appears to present new threats even without such developments. Fears about weapons of mass destruction played a part in triggering the 2003 Iraq conflict. There is a risk that in coming decades some crucial resources will cause disputes, when full attention and expenditure should be being directed to deal peacefully with environmental problems.