Since the development of well-established chemical and biological warfare programs by state entities dating from World War I, there has been a growing concern that terrorists and terrorist organizations will start using these agents. The use of chemical and biological agents by terrorists has been documented to occur as far back as 1946; however, the total incidences are few and the successes of these attacks have been limited. Very few attempts have reached fruition and the efficacy of these attacks to cause fear and economic damage are generally not equal to the damage that could have been achieved with conventional weapons on a per unit cost analysis. However, dissemination of technological information and expertise has increased the threat of chemical and biological terrorism. In this text the generally well-known chemical and biological agents are reviewed along with the weaponization and delivery methods used by states. An overview of chemical and biological terrorism in the past century is also examined and used to extrapolate what could be expected from terrorists in the future. It is found that chemical and biological terrorism are likely to be a rare event and those that will occur should have limited success. However, state-funded terrorism, weapons supplied through criminal organizations, and competent lone wolves bent on world destruction are threats that may have the most significant impact in the future.