This paper examines American policy regarding regional security arrangements (RSAs) in Asia. It argues that it is American perceptions of regional interest in such RSAs and of the compatibility of the goals of regional partners with those of the United States, which eventually shape American policy. After discussing the potential value and cost of RSAs, it suggests that actual policy choices are shaped largely as a reaction to regional states' motivations and policies. Since in Asia, there was limited functional pooling effect to be gained from RSAs, changes in American policies reflected much more a reaction to changes in regional interest in such arrangements. This interaction is demonstrated through a review of post-Cold War developments regarding US RSA policy, distinguishing between the early years of transition to unipolarity and the erosion of unipolarity since the late 1990s. These are also compared to earlier American policy regarding RSAs during the Cold War.