This paper reports the results of a study of the special export control regime for high-performance computers. The history and purpose of this export control regime are reviewed, and a framework for analysis is established, which can be used to test the basic premises on which the control regime rests and to suggest viable control thresholds. The fact that the export of certain computer systems cannot be effectively controlled is established, and the limits of controllability are defined. U.S. government applications for high-performance computers are reviewed with respect to the requirement for and criticality of such computing for national security. Finally, judgments are made as to the levels of control that are possible, and the desirability and feasibility of maintaining Such controls. Near- and intermediate-term problems that may erode the liability of the basic premises underlying high-performance computer export controls are identified.