A series of essays on the occasion of the twentieth anniversary of the Science Committee of NATO. Written by established leaders in their respective fields, some of the essays review the achievements of two decades in the basic sciences; others look at the future, with particular emphasis on the interaction of scientific progress and the needs of society. Harvey Brooks and Eugene Skolnikoff contribute a commendable chapter on science, technology and international relations, which has interesting things to say on the transfer of technology and the global distribution of research and development.