This report is part of the Youth Crime Gun Interdiction Initiative, a 17-city demonstration project aimed at reducing youth firearms violence. For the purpose of this project, a "crime gun" is defined as "any firearm that is illegally possessed, used in a crime, or suspected by enforcement officials of being used in a crime." As part of providing crime gun trace information for a 10-month period, this report contains analyses of requests for crime gun traces; analyses of successful NTC traces; analysis of incomplete traces; and analyses by adult, youth, and juvenile age categories. For the study period, Milwaukee had 4,011 crime gun trace requests to the NTC; of these, 2,762 (68.86 percent) possessors were identified. A total of 2,702 requests involved the determination of the possessor's age; there were 1,817 adult (25 years of age and over) trace requests, 656 youth (18-24 years old) trace requests, and 229 juvenile (17 years old and under) trace requests. An analysis of trace requests by type of firearm shows that the semiautomatic pistol was the most frequently traced firearm for all three age groups: 642 for adults, 370 for youth, and 119 for juveniles. Another table shows the top 10 crime guns requested for tracing by type, manufacturer, and caliber. Firearms offenses was the crime type most often associated with trace requests: 670 for adults, 352 for youth, and 155 for juveniles. The number of successful traces was 1,129 for adults, 350 for youth, 110 for juveniles, and 2,178 for all ages. Other data reported show time- to-crime rates for the top 10 crime guns requested for tracing by type, manufacturer, and caliber, as well as the most frequent source-State for successfully traced crime guns; the top State was Wisconsin for all age categories. General findings are discussed for all the participating communities and for local illegal firearms markets.