This three-year U.S.-Yugoslav cooperative research project in elementary particle physics involves three investigators in nuclear physics theory: Norma Mankoc Borstnik, Jozef Stefan Institute in Ljubljana, D. Klabucar, Rudjer Boskovic Institute in Zagreb, and Gerald Brown at State University of New York, Stony Brook. The project is divided into two parts: Mankoc-Borstnik is proposing innovative studies on the structure and constituents of the subatomic particles, quarks and leptons. Klabucar will pursue work on hadronic structure and nuclear models. The Stony Brook group will participate in both areas. This work will advance knowledge of subatomic theory and will contribute to the research efforts of major U.S. experimental groups. This project was approved by the U.S.-Yugoslav Joint Board on Cooperation in Science and Technology and is supported through a joint fund consisting of matching contributions from the governments of the United States and Yugoslavia. The U.S. contribution is provided annually by the Department of State. No NSF funds are involved. Grants are made to the principal scientific institution in Yugoslavia, but include dollar funds for U.S. scientist travel to Yugoslavia and for Yugoslav scientists' living expenses in the U.S.