Summary: The Superconducting Super Collider (SSC) will be the world's largest particle accelerator, a basic research tool for seeking fundamental knowledge about matter and energy. The Department of Energy's (DOE) cost estimate to build the SSC grew from $5.3 billion in 1987 to $8.25 billion in 1991. The SSC is not expected to produce any direct national security benefits, although national security may indirectly benefit from the potential but unpredictable practical applications of research discoveries or from technological spin-offs. Although the United States and other countries have smaller accelerators operating, no existing or planned accelerator will be exactly the same as the SSC. Known cost increases suggest that the total cost for the SSC will exceed $11 billion. To preclude the cost and schedule from continuing to increase beyond $11 billion, annual funding levels would need to increase dramatically over that projected in the President's budget. In fact, DOE is assuming in its projection that there will be no funding constraints after fiscal year 1998--an assumption that could prove unrealistic unless the budget deficit improves markedly.