The primary objective of this three-year U.S.-Yugoslav cooperative research project in physical organic chemistry between Dionis Sunko of Zagreb University and Vernon J. Shiner of Indiana University is to improve our knowledge of the mechanisms and effects of nucleophilic displacement reactions. Understanding of the theory underlying these chemical reactions are of biological and pharmacological interest. Past collaboration has been highly successful leading to many joint publications. The joint project takes advantage of the complementary stengths of the U.S. and Yugoslav research team. This project was approved by the U.S.-Yugoslav Joint Board on Cooperation in Science and Technology and is funded through a joint fund consisting of matching contributions from the U.S. and Yugoslav governments. The U.S. contribution is provided annually by the Department of State. No NSF funds are involved. Grants are made to the principal Yugoslav institute. Dollar funds are included for U.S. scientist travel to Yugoslavia and for Yugoslav scientists' living expenses in the U.S.