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There is no single definition of a gang, but there are a number of widely accepted criteria for classifying groups as gangs (Decker and Curry, 2003; Esbensen et al., 2001; Klein, 1995; Miller, 1992; Spergel, 1995). This review used the following criteria: (1) the group has three or more members, generally aged 12-24; (2) members share an identity, typically linked to a name and/or symbols; (3) members view themselves as a gang, and they are recognized by others as a gang; (4) the group has some permanence and a degree of organization; and (5) the group engages in a significant level of criminal activity. For these purposes, adult organized crime groups, hate groups, ideology groups, and militia groups were excluded.

Gangs in the United States

There were approximately 28,100 active gangs across 3,500 jurisdictions in 2009 according to law enforcement estimates. This represents an increase of more than 20 percent in both indicators since 2002 (Egley and Howell, 2011). In 2009, it was estimated that there were 731,000 gang members, a figure that is unchanged from 2002.

Gangs have been reported in all 50 states and have had a persistent presence in all cities with a population over 250,000 every year since 1996 (National Youth Gang Center, 2005). Gang problems remain the most widespread in large cities (populations of 100,000 or more) with nearly 99 percent of law enforcement agencies in these cities reporting multiple years of gang problems (National Gang Center, 2009).

One in five (20 percent) public schools reported gang activity in the school during 2007-2008 (Dinkes, et. al. 2009). In 2007, 23 percent of students ages 12–18 reported that there were gangs at their schools. Over half of schools with 1,000 or more students reported that gang activities occurred during the school year, while less than a quarter of schools with less than 1,000 students reported the problem.

Gang Membership Outcomes: Offending and Victimization

Being a member of a gang increases the likelihood of involvement in criminal activity and violent offending and being a direct or indirect victim of violent crime. Gang activity has been documented extensively to include the full range of violent and property offending, as well as drug distribution, weapons trafficking, prostitution, extortion, and other economic crimes to finance the gang (Langton, 2010).

Gang members offend at significantly higher rates than non-gang involved youth, including other delinquent "street offending" youth (Esbensen et. al., 1995). A number of studies have confirmed that gang members are significantly more likely to engage in violent, property, weapons, and drug offending than those that are not gang-involved (e.g., Battin-Pearson, et. al. 1998; Thornberry, 1998). The evidence also suggests that gang membership itself facilitates higher offending rates, as opposed to gangs simply being collections of more frequent offenders (Thornberry et. al., 2003; Zhang et. al. 1999).

Greater organization within gangs appears to lead to higher rates of offending by gang members. Members of more organized gangs report more sales of different kinds of drugs and more violent offending than do members of less organized gangs, with even incremental increases in gang organization resulting in elevated levels of offending (Decker, et. al., 2008).

Gang members are also frequent witnesses and direct victims of violence, including threats and injuries with weapons, assaults from fellow gang members and rivals, family violence, intimate partner violence, and sexual violence (Decker, Katz, & Webb, 2008; Whitman & Davis, 2007; Fleisher, 1998; Miller, 2002). In-depth interviews with female gang members revealed that sexual victimization often comes from within the gang in the form of "sexing in" initiation rituals, and ongoing sexual exploitation and other mistreatment by their male peers (Miller, 2004).

Risk Factors for Joining a Gang

Risk factors are conditions within the individual or in the physical or social environment that increase the probability that someone will join a gang. The probability for gang membership increases with the accumulation of risk factors, particularly when multiple risk factors exist across multiple domains (Howell and Egley, 2005; Hill et al., 1999; Thornberry, et. al., 2003).

Individual Risk Factors
Commonly identified individual risk factors for gang membership include early onset of delinquency (especially violence and drug use), violent victimization, including child physical abuse or child sexual abuse, and risk seeking (Howell and Egley, 2005; Esbensen, et. al. 2010; Fleisher, 2003; Miller, 2004).

Family Risk Factors
Commonly identified family risk factors for gang membership include family poverty, other gang members in the family, poor parental monitoring, and a non-two parent structure or changes in caregivers (Howell and Egley, 2005; Esbensen, et. al. 2010). For example, marital conflict and family instability were found to foster situations that reinforce aggressiveness and coercive behavior in children, which have been moderately associated with gang involvement (Williams and Van Dorn, 1999). Ethnographic research characterized the families of gang kids, compared with those of non-gang affiliated kids, to be more extreme in disorganization and conflict, including child abuse and neglect, which is further exacerbated by parent's drug use, criminal behavior, and low income (Fleisher, 2003).

Peer Group Risk Factors
The most commonly identified peer level risk factor for gang membership is association with delinquent or gang involved peers (Howell and Egley, 2005; Esbensen, et. al. 2010). For example, youth with non-delinquent peers committed an average of 1.6 self-reported acts of violent delinquency during a year, while youth with delinquent peers committed an average of 5.1 violent acts; gang members committed an average of more than 11 violent acts (Battin-Pearson et al., 1998).

School Risk Factors
Commonly identified school risk factors for gang membership include low commitment to school, low achievement, low aspirations, perceived lack of safety in school, and frequent truancy, suspensions, or expulsions (Howell and Egley, 2005; Esbensen, et. al. 2009; National Youth Gang Center, 2011).

Community Risk Factors
Commonly identified community risk factors for gang membership include poverty, presence of gangs, availability of drugs, perceived lack of safety, low neighborhood attachment, high community arrest rates, and availability of firearms (Hill, Howell, Hawkins, et al., 1999; Hill, Lui, and Hawkins, 2001; Howell and Egley, 2005; Lizotte, Krohn, Howell, et al., 2000).

Program and Practice Findings

As described above, the factors leading an individual to join a gang tend to be a complex mixture of individual, family, peer group, school, and community characteristics. Similarly, the harmful outcomes and consequences of gang membership impact the individual, family, peer group, school, and community. Gang prevention, intervention, and enforcement approaches have taken on a similar scope and diversity with various levels of emphasis on law enforcement and criminal prosecution, individual and family therapeutic, social systems, public health, and community empowerment orientations.

CrimeSolutions.ojp.gov identifies a number of evidence-based programs that are "promising" and "effective" at addressing issues related to gangs. Efforts are ongoing to identify and integrate a wider range of effective gang prevention, intervention, and enforcement practices. The National Gang Center identifies a number of principles and characteristics found to be associated with successful practices:

  • Conducting local gang problem assessments to help target programs, services, and enforcement activities to the right neighborhoods, families, gangs, and individuals
  • Using a coordinated mix of prevention, intervention, enforcement, and reentry programs and strategies to improve the chances for both near term and long term success in reducing gang activity
  • Building trust between prevention, intervention, and enforcement professionals and building a common vision that is shared with community members
  • Developing and maintaining a local steering committee with executive authority to make organizational changes if necessary to improve community response to gangs
  • Activating operational teams for each strategy (prevention, intervention, enforcement, reentry) that coordinate activities and share information with the steering committee. (National Gang Center, 2010)


Battin-Pearson, S. R., Thornberry, T. P., Hawkins, J. D., and Krohn, M. D. 1998. "Gang Membership, Delinquent Peers, and Delinquent Behavior." Juvenile Justice Bulletin. Youth Gang Series. Washington, D.C.: U.S. Department of Justice, Office of Justice Programs, Office of Juvenile Justice and Delinquency Prevention.

Decker, S. H., Katz, C. M., & Webb, V. J. 2008. "Understanding the black box of gang organization: Implications for involvement in violent crime, drug sales, and violent victimization." Crime & Delinquency, 54(1), 153-172.

Dinkes, R., Kemp, J., and Baum, K. 2009. Indicators of School Crime and Safety: 2009. Washington, D.C.: National Center for Education Statistics, Institute of Education Sciences, U.S. Department of Education, and Bureau of Justice Statistics, Office of Justice Programs, U.S. Department of Justice.

Egley, A., Jr., and Howell, J.C. 2011. Highlights of the 2009 National Youth Gang Survey. Fact Sheet. Washington, D.C.: U.S. Department of Justice, Office of Justice Programs, Office of Juvenile Justice and Delinquency Prevention.

Esbensen, F. A., Huizinga, D., & Weiher, A. W. 1995. "Gang and non-gang youth: Differences in explanatory factors." In M. Klein, C. L. Maxson & J. Miller (Eds.), Modern Gang Reader (1 ed., pp. 192-201). Oxford: Oxford University Press.

Esbensen, F. A.; Peterson, D.; Taylor, T. J.; and Freng, A. 2009. "Similarities and Differences in Risk Factors for Violent Offending and Gang Membership." Australian and New Zealand Journal of Criminology, 42:1–26.

Fleisher, M.S. 1998. Dead End Kids: Gang Girls and the Boys They Know. Madison, Wisconsin: University of Wisconsin Press.

Fleisher, M. 2003. "Lost Youth and the Futility of Deterrence." In S. McConville (Ed.), Use of Punishment (pp. 26-102). Devon: Willan Publishing.

Hill, K. G.; Howell, J. C.; Hawkins, J. D.; and Battin-Pearson, S. R. 1999. "Childhood Risk Factors for Adolescent Gang Membership: Results From the Seattle Social Development Project." Journal of Research in Crime and Delinquency, 36(3):300–322.

Hill, K. G.; Lui, C.; and Hawkins, J. D. 2001. "Early Precursors of Gang Membership: A Study of Seattle Youth." Juvenile Justice Bulletin. Washington, D.C.: U.S. Department of Justice, Office of Juvenile Justice and Delinquency Prevention.

Howell, J. C. and Egley, A., Jr. 2005. "Moving risk factors into developmental theories of gang membership." Youth Violence and Juvenile Justice, 3(4), 334-354.

Langton, L. 2010. Census of Law Enforcement Gang Units, 2007: Gang Units in Large Local Law Enforcement Agencies. Washington, D.C.: U.S. Department of Justice. Bureau of Justice Statistics.

Lizotte, A. J.; Krohn, M. D.; Howell, J. C.; Tobin, K.; and Howard, G. J. 2000. "Factors Influencing Gun Carrying Among Young Urban Males Over the Adolescent-Young Adult Life Course." Criminology, 38(3):811–834.

Miller, J. 2004. "Gender and Victimization Risk Among Young Women in Gangs." In R. D. Peterson (Ed.), Understanding Contemporary Gangs in America: An Interdisciplinary Approach. Upper Saddle River, N.J.: Prentice Hall.

Miller, J. 2002. "Young Women in Street Gangs: Risk Factors, Delinquency, and Victimization Risk." In W.L. Reed & S. H. Decker (Eds.), Responding to Gangs: Evaluation and Research (pp. 66-105). Washington, D.C.: U.S. Department of Justice Office of Justice Programs.

National Gang Center. 2010. Best Practices to Address Community Gang Problems: OJJDP's Comprehensive Gang Model, Second Edition. Washington, D.C.: U.S. Department of Justice, Office of Juvenile Justice and Delinquency Prevention.

National Youth Gang Center. 2011. OJJDP Strategic Planning Tool. Retrieved January 9, 2011 from https://www.nationalgangcenter.gov/SPT/.

National Youth Gang Center. 2005. National Youth Gang Survey Analysis. Retrieved September 29, 2010 from http://www.nationalgangcenter.gov/Survey-Analysis.

National Youth Gang Center. 2009. National Youth Gang Survey Analysis. Retrieved September 29, 2010 from http://www.nationalgangcenter.gov/Survey-Analysis.

Thornberry, T. P. 1998. "Membership in youth gangs and involvement in serious and violent offending." In R. Loeber and D. P. Farrington (eds) Serious & violent juvenile offenders: Risk factors and successful interventions, 147–66. London: Sage.

Thornberry, T. P.; Krohn, M. D.; Lizotte, A. J.; Smith, C. A.; and Tobin, K. 2003. Gangs and Delinquency in Developmental Perspective. New York, N.Y.: Cambridge University Press.

Williams, J. H., & Van Dorn, R. A. 1999. "Delinquency, Gangs, and Youth Violence." In J. M. Jenson & M.O Howard (Eds.), Youth Violence: Current Research and Recent Practice Innovations (pp. 199-228). Washington, D.C. NASW Press.

Whitman, J. L., & Davis, R. C. 2007. Snitches Get Stitches: Youth, Gangs, and Witness Intimidation in Massachusetts. Washington, D.C.: National Center for Victims of Crime.

Zhang, L., Welte, J. W., & Wieczorek, W. F. 1999. "Youth gangs, drug use, and delinquency." Journal of Criminal Justice, 27(2), 101.

Date Published: January 8, 2020