The study found that one third of the sample of incarcerated felons reported gang involvement prior to incarceration, and that this involvement was associated with increased levels of crime and delinquency, increased association with delinquent/crime involved friends, and significantly increased levels of delinquent attitudes. Analysis also found a high degree of variation in the type of gang involvement, with individuals involved with organized/criminal gangs at the time of incarceration experiencing significantly more serious misconduct while in prison. Data for this study were obtained from a sample of 504 young adults incarcerated in a large Midwestern State prison in 1996. The study examined the prevalence and different types of pre-incarceration gang membership among the inmates and explored if and how this involvement affected the behavior of the inmates. The results of the study indicate that pre-incarceration gang involvement for young offenders is a significant risk factor for prison misconduct, and for the development of a prosocial identity after release from prison. Implications for future research are discussed. Tables, appendix, notes, and references