Foreign official holdings of U.S. Treasuries increased from $400 billion in January 1994 to about $3 trillion in June 2010. Most of this growth is accounted for by a handful of emerging market economies that have been running large current account surpluses. These countries are channeling their savings through the official sector, which is then acquiring foreign exchange reserves. Any shift in policy to reduce their current account surpluses or dampen the rate of reserves accumulation would likely slow the pace of foreign official purchases of U.S. Treasuries. Would such a slowing of foreign official purchases of Treasury notes and bonds affect long-term Treasury yields? Most likely yes, and the effects appear to be large. By our estimates, if foreign official inflows into U.S. Treasuries were to decrease in a given month by $100 billion, 5-year Treasury rates would rise by about 40-60 basis points in the short run. But once we allow foreign private investors to react to the yield change induced by the shock to foreign official inflows, the long-run effect is about 20 basis points.