Abstract : The proliferation of short-range ballistic missiles in the world today poses a direct, immediate threat to many of our allies and to some U.S. forces deployed abroad in defense of our national interests. Over time, the proliferation of longer range missiles could pose a greater threat to the U.S. itself. For these reasons, an active national missile defense is playing a central and vital role in U.S. defense planning well into the next century. I would characterize the last three years as a period of transition for our national missile defense program. We are moving from a culture of research, demonstrations and space experiments to one of developing and being prepared to field an operational capability. It takes a different kind of discipline to move from what was essentially an RD deterring the threat; and defending against the threat.