The governments of the Republic of Korea and the United States over the past 40 years have made commitments to build a cooperative relationship in S&T that serves both political and scientific goals. The policy commitment has resulted in a strong S&T relationship. Partly as a result of this commitment, and partly due to Korea's aggressive investments into research and development (R&D) spending, Korean capacity to conduct world-class R&D now puts it among the top countries in the world. Both governments have made significant financial commitments to bilateral S&T cooperation. The Korean government's part in this effort has included investments in joint projects with the United States, supported by a policy of strong domestic investment in R&D. The United States government has provided both development assistance (now terminated) and special grant programs to build scientific capacity in Korea and to encourage cooperation. Thousands of Korean students have studied S&T in the United States. The bilateral S&T relationship has grown in an environment where international S&T cooperation is growing overall: Promoting cooperation is becoming a more important part of the S&T policies of most advanced and many developing countries. The network resulting from international cooperation in science is creating a system that is transcending the actions and direct influence of individual nations, and taking on a global character. This shift in the gravity centers of science has implications for the bilateral relationship as well as Korea's and the United States' relationship with other countries. The enhanced scientific capacity of Korea, the changing structure of international science, and shifts in the role of the United States in it, suggest that a reexamination of the relationship is in order. The most robust cooperation grows from the "bottom up"-scientists linking with each other and identifying important areas of common interest and concern and this should be considered as the focus of the Korea-U.S. relationship. More importantly, while it may be useful to continue to seek bilateral ties, international cooperation is more often taking on a multinational character. This suggests that a focus on a bilateral relationship may be too narrow: the two countries should look together at ways to link (jointly or separately) with other partners. A review of complementarities may also identify important areas where the two countries should work together.