The basic idea of common security is not complex. It is that no country can obtain security, in the long run, simply by taking unilateral decisions about its own military forces. This is because security depends also on the actions and reactions of potential adversaries. Security has to be found in common with those adversaries. These ideas were considered in a SIPRI conference held in 1983. The conference had two main objectives. The first was to undertake a critical examination of the concept. The second was to consider the implications of the idea for policy in general, and for disarmament and arms control policy in particular. Originally published in 1985, this book contains revised versions of some of the papers presented at the conference.