The Kansas City (MO) Gun Experiment was an experiment conducted with the purpose of reducing gun violence, unauthorized shootings and homicides. The project was evaluated by the Department of Criminology, the University of Maryland, the Department of Criminal Justice and the University of Texas. The program lasted for 29 weeks (July 1992–January 1993); during this time the Kansas City Police Department increased the number of police patrols in areas where gun crimes and homicides were more likely to occur (patrol beat 144 and patrol beat 242).

The experiment was deemed promising and somewhat successful, as there were a lot less gun crimes and the homicide rate declined in the targeted areas; however, there was no significant effect on other crimes. Due to its properties, the Kansas City Gun Experiments is considered a longitudinal study.

The main hypothesis of the experiment was that there is a close relation between gun violence and gun seizures; if officers seize weapons, the violent perpetrators in possession of those weapons might become discouraged and stop carrying guns in order to avoid arrest. Thus, the gun violence and the homicide rate would drop, due to the increased law enforcement presence in the areas, as well as the gun seizing strategy. The close connection between the two variables (gun seizures and gun violence) indicates a higher construct validity.

While we can determine that the experiment possessed internal validity, we cannot say the same about its external validity, as we cannot conclude whether the experiment might be successful in different places other than the targeted areas because the project was never repeated. If a similar research is to be conducted again, the analysts should take the demographics of the place into consideration; perhaps only a place with similar population properties such as Kansas City can generate the same or similar results.