On November 25, 1969, President Nixon made a major statement on United States chemical and biological warfare (CBW) policies. He reaffirmed the renunciation of the first use of lethal chemical agents and extended this policy to incapacitating chemical agents. He also banned the offensive use of lethal and incapacitating biological agents, promised the destruction of biological agent stockpiles and confined biological research to defensive measures such as immunization. The President's announcement followed a six month review of CBW policies by the National Security Council. The policy statement met with generally favorable reaction in the United States and abroad. Although many people were uncertain as to why the President chose to ban biological weapons completely and not chemical weapons, such a significant unilateral step in the direction of arms control was felt to be a positive step toward peace. The purpose of this unclassified study is to investigate the events that preceded the CBW policy statement in order to identify and evaluate the factors which contribute to the specific decision to ban biological weapons. Little has been written on why biological weapons were banned and it is hoped that this study will shed light on the reasons for the ban.