The distinction made in what is popularly called the dirty bomb is expressly designed to have an enhanced, destructive or disruptive potential by reason of the introduction into its manufacture of elements intended to contaminate the environment of the explosion for that specific purpose. A dirty bomb in the generic sense can be constructed so as to disperse any dangerous, toxic, chemical or biological material. Dirty bombs are also referred to as Radiological Dispersal Devices (RDD). In developing countermeasures, it is necessary to focus and understand the term dirty bomb and its intent as a threat in its use as an act of terrorism. This article attempts to offer clarification of dirty bombs in the areas of the construction of dirty bombs, the intent in the use of a dirty bomb, a profile of those who would attempt to use a dirty bomb, and what countermeasures can be taken to prevent the use of a dirty bomb.