The September 11 attacks forcefully brought home the need to better protect the U.S. homeland. But how can this be accomplished most effectively? Here, a team of Brookings scholars offers a four-tier plan to guide and bolster the efforts under way by the Bush administration and Congress. There has been some progress in making our homeland more secure. But the authors are concerned that the Bush administration may focus too narrowly on preventing attacks like those of the recent past and believe a broader and more structured approach to ensuring homeland security is needed. Given the vulnerability of our open society, the authors recommend four clear lines of direction. The first and last have received a good deal of attention from the Bush administration, though not yet enough; for the other two, a great deal remains to be done: Perimeter defense at the border to prevent entry by potential perpetrators and the weapons and hazardous materials they may use Prevention by detecting possible terrorists within the United States and securing dangerous materials they might obtain here Identification and defense of key sites within the county: population centers, critical economic assets and infrastructure, and locations of key political or symbolic importance Consequence management to give those directly involved in responding to an attack that may nevertheless occur the tools necessary to quickly identify and attack and limit its damage Included are specific recommendations on how much more to spend on homeland security, how much of the cost should be borne by the private sector, and how to structure the federal government to make the responsible agencies more efficient in addressing security concerns. Specifically, the authors believe that annual federal spending on homeland security may need to grow to about $45 billion, relative to a 2001 level of less than $20 billion and a Bush administration proposed budget for 2003 of $38 billion. They also