Major findings from this report regarding the level of gang activity in Maricopa County, AZ in 2009 include: 16 of the 20 law enforcement jurisdictions that responded to the survey indicated an active gang presence in their jurisdictions; 15 of the reporting agencies estimated active gang membership to be 20,768 members, and more than half of the reporting agencies indicated that gangs were expanding their membership and their scope of activities; assault/aggravated assault was listed as the primary crime committed by gangs, followed by burglary and drug sales; 40 percent of responding agencies indicated a high level of gang involvement in the distribution of illegal drugs; and enforcement and identification of gang members were identified as the most effective gang intervention strategies used in the county. This report from the Arizona Criminal Justice Commission presents the 2009 gang threat assessment for Maricopa County, AZ. Law enforcement agencies in the county were surveyed in the spring of 2010 to determine the level of gang activity in their county. The survey is modeled after the National Gang Threat Assessment and contains questions for law enforcement agencies dealing with the presence of gangs within their jurisdictions, the level of gang activity, the involvement of gang members in crime and illegal drug distribution, the extent of cross-gang coordination, and law enforcement strategies targeting gang members. Tables and figures