This thesis examines self-identified gang members and extremists incarcerated in Navy and Marine Corps brigs and disciplinary barracks. Information was gathered from interviews conducted with inmates. The interviews focused on several key issues, including reasons for enlisting in the Navy and Marine Corps; truthfulness with recruiters concerning certain illegal activities prior to enlistment, including juvenile arrests and convictions; the nature and severity of crimes for which members were convicted, including links with gangs or extremist groups; and reasons for lack of assimilation and acculturation into military service. This thesis also provides background information on present enlistment screening procedures, current Department of Defense policies concerning gangs and extremist groups, and demographic data on the characteristics of self- admitted gang members who are incarcerated in a Navy brig. Common themes that emerged from the interviews are presented, and selected summaries are included in an appendix. In addition, the study examines enlistment screening procedures for identifying applicants who have gang or extremist group affiliations, and recommends a number of areas for farther research.