The case analysis presented here will help us develop the most effective possible enforcement strategies. This report demonstrates the effectiveness of State and local law enforcement agencies and prosecutors joining ATF in "following the crime gun" to the gun's illegal supplier, and targeting that supplier and others in the chain of illegal transfers. It may be the gun of the drug dealer, the violent gang member, the repeat felon, parolee or probationer, the domestic violence offender, the juvenile, or any other person prohibited from possessing a firearm. Gun traffickers are often criminals in other respects, and trafficking investigations provide another means to prevent them from harming the community. The analysis documents an aggressive, productive effort that led to the prosecution, conviction, and sentencing of hundreds of firearms traffickers during this period. It also suggests that this effort could be rendered still more effective with continued improvements in investigative techniques and enforcement tools.