Over the past three decades, there has been a noted increase in hostage and barricade incidents involving perpetrators with a variety of emotional, economic, and political motives. A hostage incident may be defined as an incident in which (a) perpetrator(s) hold(s) one or more persons against their will in a location known to police. A barricade incident, on the other hand, is an incident without hostages in which a perpetrator is barricaded, also in a location known to police and refusing to surrender. Approximately 25 years ago, a theory of crisis/hostage negotiations was developed which has been continuously refined in field applications. This article will define the goal of crisis/hostage negotiation, review the history of hostage taking from biblical times to the present, review the utilization of psychologists and other mental health consultants by police crisis/hostage negotiation teams, and discuss the four roles and related functions of psychologists on crisis/hostage negotiation teams.