This article examines one facet—arms control—of a larger puzzle in US-China relations over the last decade, namely why are we seeing an increasing degree of politico-military friction in Sino-US relations as China becomes more, not less, integrated into global institutions? On the one hand China’s arms control performance on most issues improved over the 1990s, with participation rates increasing in various institutions, agreements and regimes, and with accession to a small number of commitments that could actually constrain China’s relative power to some degree. On the other, despite these trends Sino-US differences over arms control have remain acute and a source of friction in the relationship. What is going on? This article begins with a description of the changes in Chinese arms control behavior over the last decade or so and offers a range of possible explanations for these. It then examines the areas of disagreement and friction in the US-China relationship on arms control. In particular it focuses on the apparent differences in the preferences of US and Chinese decision-makers on arms control policy. Finally it offers a list of three major explanations for these differences.