Determining a sufficient reactionary gap for a police officer to successfully defend against a knife attack is crucial to police officer survival. Recognizing the success of the police officer depends on his or her distance from the attacker and reaction time, a test was conducted to determine if the 21-foot rule provided an adequate reactionary gap to draw a firearm, fire, and survive the attack. Participants included 128 law enforcement and corrections basic recruits at the George Stone Criminal Justice Training Center in Pensacola, Florida, during the 1995-1997 period. Students were placed in a square in the middle of a room and were equipped with standard duty gear, including a pistol belt, a holster, and a training firearm. They were attacked by one of two assailants 45 degrees off either front flank at distances of 3, 5, 10, 15, and 21 feet. Students were instructed to start in an interview stance; when attacked, they were to draw, fire two rounds center mass, and then move out of the way to avoid the attacker's momentum. Results showed that distance had an effect on survival. Because only 9 of the 128 students survived the attack, it was determined that drawing and firing a handgun as a defense against a knife attack before using defensive tactics was a deadly choice. 1 table, 1 chart, and 10 photographs