This project partially supports the research visits of U.S. scholars in the mathematical sciences and in theoretical physics to the Institute des Hautes Etudes Scientifiques in France. This international institute is comparable to the Institute for Advanced Study at Princeton and, in addition to National Science Foundation support, is supported in part by science agencies in a number of other nations. The U.S. visitor support in this project will cover approximately 40 per cent of the cost of the U. S. scientists studying at the Institute and includes support for both senior and young post-doctoral investigators. Recent and ongoing research at the institute includes algebraic geometry, differential geometry, dynamical systems, infinite dimensional groups and physics, crystallography, statistical mechanics, and quantum field theory.