Participants at the COST Interaction Conference, held in Basle, Switzerland, on 9-11 October 1995 recommended the reinforcement of COST and its extension to new scientific disciplines. Following three days of intense discussion, involving 600 researchers and representatives of research institutions and public administrations, a number of respected scientific and political personalities (including three Nobel Prize winners) were invited to participate in a round table discussion concerning COST. This discussion clearly underlined the importance of reinforcing this method of European research cooperation. Participants, however, expressed the wish to see a better definition of COST in order to ensure greater complementarity with other European research programmes (notably EUREKA and the Fourth Framework Programme of the European Union). They, nevertheless, insisted on preserving the basic principles of COST: the variety of disciplines; the bottom-up approach (leaving the initiative to the scientific partners); national financing; and non-bureaucratic structures. The participants further stressed the fundamental importance of COST and its pioneering role for pan-European research, particularly for the integration of the research carried out in the countries of Central and Eastern Europe. They noted in particular the decisive role played by COST in the establishment of a partnership between the scientists of all 25 COST Member countries and stressed the low financial input required to produce significant results within the COST system. The conclusions of this conference shall be taken up at the next COST Ministerial Conference scheduled for 1996.