This report summarizes a joint study by RAND and the Korean Institute for Defense Analyses (KIDA) on U.S.-Korean force planning and the sharing of roles and burdens in the 1990s. It considers possible changes in the forces and burdens of the allies in view of the changing strategic environment, altered economic and technological capabilities, and political constraints, while maintaining a durable alliance. The study identifies alternative security environments and conflict contingencies and draws from them policy guidelines for combined military planning. It then assesses the relative changes in U.S. and Korean economic and technological capabilities as well as the resource constraints faced by the allies. It focuses on alternative Korean and U.S. force structures, roles, command relationships, and cost implications. Among other things, the authors conclude that (1) the United States and South Korea should reaffirm the mutual importance of their alliance, (2) the two allies should formally declare that they intend South Korea to be principally responsible for its own defense by the year 2000, and (3) this intention should be gradually implemented consistent with South Korea's force improvement and progress in inter-Korean relations.