The increasing size and international character of many defence companies and the growing development of dual use technologies for both military and civil purposes poses a number of important questions: does defence industry have a distinct identity; if so, what are its defining features; to what extent does a country need a defence industry; and how should governments interact with defence companies? By considering the contribution of defence industry to the delivery of national security in a number of selected countries, this paper seeks to throw light on these questions at a time when the