Findings support the study’s central hypothesis that traditional cultural values are protective for Mexican-origin youth; the interaction between familism values and deviant peer affiliation was not significant using maternal and paternal reports of adolescent externalizing behaviors. Greater exposure to deviant peers was consistently associated with increased youth externalizing problems, supporting extensive literature documenting relations between deviant peer affiliations and youth conduct problems. However, the negative impact of deviant peer affiliations on adolescent externalizing behavior was attenuated by adolescent, maternal, and paternal familism values in five of six models that were tested with teacher reports of externalizing behaviors. Data were collected from 598 seventh grade students of Mexican origin and their parents who were recruited as part of an intervention study from 5 junior high schools. Tables, figure, note, and references