Context: Homicide is a leading cause of death in Colombia, with much of the fatal interpersonal violence concentrated in the country's largest cities. Firearms are involved in as much as 80% of homicides in Colombia.
Objective: To evaluate the effect of an intermittent police-enforced ban on carrying firearms on the incidence of homicide in urban Colombia.
Design: Interrupted time-series study with multiple replications.
Setting: Cali, Colombia, during 1993 and 1994 and Bogotá, Colombia, from 1995 through August 1997.
Participants: The populations of Cali and Bogotá.
Intervention: Carrying of firearms was banned on weekends after paydays, on holidays, and on election days. Enforcement included establishment of police checkpoints and searching of individuals during traffic stops and other routine law enforcement activity.
Main outcome measure: Homicide rates during intervention days were compared with rates during similar days without the intervention; estimates were based on comparisons within the same month, day of week, and time of day.
Results: There were 4078 homicides in Cali during 1993 and 1994 (114.6 per 100,000 person-years). In Bogotá, 9106 homicides occurred from 1995 through August 1997 (61 per 100,000 person-years). The incidence of homicide was lower during periods when the firearm-carrying ban was in effect compared with other periods (multivariate-adjusted rate ratio, 0.86 [95% confidence interval [CI], 0.76-0.97] for Cali, and 0.87 [95% CI, 0.77-0.98] for Bogotá).
Conclusion: An intermittent citywide ban on the carrying of firearms in 2 Colombian cities was associated with a reduction in homicide rates for both cities.