Professor Zare, Associate Fellow of TWAS, Academy of Sciences for the Developing WorldI assert that the scientific community is and ought to be an international one. It should be treasured as a powerful means of improving the world. In these days of world-wide economic turbulence and intense competition among nations, it is easy to question why the scientific establishment should cooperate across national boundaries. Let me present a few arguments why I believe the need for international scientific cooperation is more compelling than ever before. Some of these thoughts have already been expressed in an editorial published in Angew. Chem. Int. Ed. 2011, 50, 8202 8203.Many problems facing humanity, such as climate change, hunger, environmental sustainability, and pandemics, are global by nature. Thus, they require a global approach to their solution. We need scientists from all countries to work together on such problems. The solutions to these problems will be indispensible to our future on this planet. Moreover, advances in communications make it possible to enter into collaborations that previously were unthinkable.The scientific enterprise benefits by sharing what is learned. It is true that if you have food and a beggar asks you for some, feeding the beggar leaves you with less food. But in contrast, if someone asks you to share your knowledge with them, more often than not, both parties are enriched by the transaction. Indeed, this is one of the secret benefits of teaching the teacher also learns.I reject the notion that science is a zero-sum game. In a zero-sum game, such as the game of chess which I love, there must be a loser for every winner. If a country has enough talent to recognize a scientific advance coupled with a sufficiently advanced technological base to turn the advance into practice, then a scientific advance made anywhere in the world can lead to global economic gain. A country need not be first in all scientific disciplines to benefit from advances. Many other factors, from entrepreneurial spirit to a skilled workforce, can transform scientific advances made in other countries into societal benefits.When two countries wish to strengthen their relations, they often call for meetings between the military leaders of the two countries. It seems to me that much more effective in establishing good relations is a meeting of the scientific leaders. Scientific cooperation promotes general friendship and mutual understanding as well as common values and standards. History teaches us that relations between countries have their political ups and downs. We gain so much in smoothing out the bumps by having people in each country who know and trust each other. In this sense, having strong scientific ties between various countries is simply good diplomacy.A IMPORTANCIA DA COOPERACAO CIENTIFICA INTERNACIONAL by Richard N. Zare, Department of Chemistry, Stanford University, Stanford, California 94305-5080 USAProfessor Zare, Membro Associado da TWAS, Academia de Ciencias para o Mundo em DesenvolvimentoAfirmo que a comunidade cientifica e e deve ter caracter internacional. Ela deve ser protegida como um poderoso meio de melhorar o mundo. Nestes dias de turbulencia economica, no mundo todo, e competicao intensa entre