The study reviewed mental health and probation files for 122 adolescent males convicted of criminal offenses and investigated demographic, behavioral, familial, school related, and crime related variables; a detailed profile of a juvenile gang member emerged. Ethnicity, alcohol and drug abuse, depressive disorder, violent conviction, age at first conviction, and total number of convictions differed significantly between groups of delinquent gang and non-gang members. A discriminant analysis demonstrated that Hispanic ethnicity, alcohol and drug abuse, as well as age at first conviction were the best predictors of gang membership. In summary, the study disclosed that juvenile gang members become involved in crime at a very early age and engage in continuous criminal behavior; are convicted of more violent offenses than are non-gang members; and are more likely to abuse alcohol and drugs. The data for this study were collected in one county, a county in which Hispanic gangs are prominent, and generalizability of findings may be questionable. Figure, tables, references