The first presentation consists of statistics on law enforcement officials' assessments of gang problems in their jurisdictions and a brief discussion of techniques for gathering such data. A major problem in gathering data on gangs and gang activities is the lack of uniformity in definition of terms. Law enforcement officials generally have the broadest knowledge of gang activities, but social service providers' knowledge is deeper, i.e., they have detailed knowledge of activities in their area of the city, but little knowledge about the rest of the city. An aspect of gang activities that is receiving considerable attention is gang migration, the movement of gangs or gang members from one geographic area to another. Gang migration may be a social response (family or friends in the new area), or an attempt to establish drug-related enterprises in a new area. Further research is needed on whether migratory gangs require different intervention/prevention strategies. There is no evidence that gang migration results in gang proliferation. A report on one gang violence reduction program also contains statistics on gang intervention and suppression efforts.