Mail or parcel bombs, or other dangerous devices or substances, may be routed through the United States mail service in order to harm an intended victim. Usually, these mail bombs are not the work of international terrorists, but rather the work of disgruntled persons who seek retribution for perceived wrongs. The article describes how to recognize potentially dangerous letters and parcels in order to avoid death or injury. First, the sender of the mail bomb is generally careful to ensure only the intended victim opens the parcel; as such, markings on the parcel that indicate only one person should open the parcel, markings such as “personal” or “confidential,” are one clue to the dangerousness of the contents. Another indicator that one should be careful of a parcel is the presence of strange odors or sounds emanating from the package. Unusual markings such as, “open this end only,” are another clue that an explosive device may be contained inside a parcel. Any evidence of a powder or granular substance is further evidence that caution should be exercised. Other clues include the absence of a return address, no return address, excessive postage, or unusually shaped packages. The author cautions that when a mail bomb is suspected, it is crucial to never move, pick up, or try to open the package. Finally, it is important to document observations of the package and actions taken in regard to the package in order to create a written record from which to learn. References