The illegal trafficking of small arms is becoming an increasing problem both nationally and internationally. The NTC, which is the only program of its kind in the world, is relied upon by the national and international communities to trace the history of guns used in the commission of crimes. Part of its mission is to combat the illegal movement of United States firearms across international borders. The NTC stores information about firearm sales, suspect guns, stolen firearms, firearms with obliterated or partial serial numbers, and records of Federal firearms licensees who are no longer in business. The article explains how traces are conducted and also points out that 9 out of 10 traced firearms are manufactured in the United States. The National Tracing Branch (NTB), an arm of the NTC, has developed programs designed to provide a comprehensive approach to firearm tracing. The article explains some of these programs and concludes that ATF’s commitment to support law enforcement efforts has become an ever-expanding global effort.