The findings show that student social networks in the school setting were composed of a complex mixture of nondelinquents, minor delinquents, and serious delinquents ("birds of different feathers") instead of being composed of students who engage in similar behaviors ("birds of a feather flock together"). Delinquent students, whether minor or serious, were slightly more popular and important in their social networks than nondelinquents; however, analyses in which same gender (all boys or all girls) and cross-gender (boys and girls together) were distinguished suggest that these difference were mainly the result of cross-gender friendships; i.e., delinquent boys are more popular than nondelinquent boys among girls. These findings imply that many law-abiding adolescents are exposed to delinquent examples in the school setting and vice versa; and minor offenders interact with serious delinquents. What this means for the molding of behaviors is unclear and should be the subject of future research. The sample consisted of 1,730 students (44 percent girls) in their first and third years in 11 schools. The analysis of the composition of student social networks derived from questions about the students with whom respondents spent a lot of time (up to 10 fellow students could be identified) and with whom they spent the most time ("best friends"). This enabled the mapping of social networks of friends and best friends. Data on delinquent behavior were collected with self-report questions on involvement in 12 offenses during the past school year. Correlations were computed between a respondent's own delinquency scores and the average scores of the friends and best friends they had chosen. 5 tables, 3 figures, and 53 references