The introduction of the euro is expected to increase capital mobility in Euroland. While, as in the US, a common monetary policy is now performed, institutional structures are inherently more heterogenous. This paper argues that experience of the US with financial market integration can potentially serve as a benchmark for the integration effects. The paper finds that, despite the restrictions to the regional expansion of banks that have prevailed, the degree of financial integration within the US tends to exceed that within Europe. Implications of barriers to the free mobility of capital for monetary policy and banking supervision are discussed.