The Strategic Defense Initiative (SDI) is a research program in which President Reagan asked key scientists and technological leaders to conduct research aimed at determining whether there are cost-effective defensive technologies that could improve the deterrent capability of the United States and allies. The concept of the SDI program envisions a layered defense where hostile missiles could be attacked shortly after launch during the boost and postboost phase, individual attack on the warheads themselves or attack as they approach the end of their flight. Standard arguments for and against the SDI program were examined. Information was gathered using a review of the literature and through analysis of the views of key military and civilian leaders. While it has been argued that a US SDI program will cause instability rather than promote stability, it must be realized that the Soviet Union has been emphasizing defense and survivability and has been pursuing an extensive SDI program for many years. The SDI program facilitated dialogue and negotiations between the United States and the Soviet Union as well as has the potential to enhance our basic defense strategy of deterrence. The program was in part responsible for the successful Geneva Summit meetings in November 1985. The US Congress, the elections of 1988 and US public opinion will play a significant role in the future of the SDI program.