The Advanced Research Institute (ARI) on The Application of Systems Science to Energy Policy Planning was held under the auspices of the NATO Special Programme Panel on Systems Science in collaboration with the National Center for Analysis of Energy Sys tems, Brookhaven National Laboratory, USA, as a part of the NATO Science Committee's continuous effort to promote the advancement of science through international cooperation. Advanced Research Institutes are sponsored by the NATO Science Committee for the purposes of bringing together senior scientists to seek consensus on an assessment of the present state of knowl edge on a specific topic and to make recommendations for future research directions. Meetings are structured to encourage inten sive group discussion. Invitees are carefully selected so that the group as a whole will contain the experience and expertise neces sary to make the conclusions valid and significant. A final report is published presenting the various viewpoints and conclusions. The NATO Systems Science Panel noted that the systems approach is increasingly being applied to energy policy analysis and plan ning in both public and private sectors of national economies. Consequently, it seemed appropriate at this time to bring together experts to review and evaluate recent experience, in order to iden tify strengths and weaknesses in current prac tice, and to make recommendations for research directions.