This paper argues that traditional arms control approaches no longer work well for even traditional security problems on the U.S.-Chinese security agenda for three reasons: Firstly, even when both states reason for arms control from the superpowers’ experience during the Cold War, they do so in different ways; secondly, a growing number of experts and policy elite in both countries do not think the benefits of formal arms control outweigh the costs and risks; and thirdly, those who think formal arms control has an important role to play lack a clear and compelling logic for why arms control is durable and achievable among highly interdependent states with unequal power, mixed interests, and dissimilar values. Past attempts find a new basis for U.S.-China security cooperation—e.g., by using voluntary measures or by relying on the economic interdependence of the two states—have proved insufficient. The second half of this paper suggests the basic elements of a cooperative security logic that could be a more appropriate and effective basis for cooperation. Instead of narrowly defining the objective of arms control as increasing deterrence stability at lower cost and risk, this logic aims more broadly to prevent threats from developing, provide reassurance, and promote consensual political order among states. Rather than trying primarily to set equal technical limitations on military capabilities, dialogue and negotiations should seek to ensure that whatever capabilities states have, including asymmetrical and dual-use ones, are used for mutually acceptable purposes and according to equitable behavioral rules. Issues related to transparency, verification, and compliance management would also be handled in ways that promote cooperation rather than competition. The paper concludes by examining how U.S.-Chinese cooperation in space, on nuclear weapons issues (including the Comprehensive Test Ban Treaty), and on missile defense all stand to benefit from reliance on this new logic.