Substance use among Mexican origin, low-income youths is a serious, but under-studied problem. This study examines the relationship between the structure of Mexican origin families (i.e. nuclear, single-parent, blended or extended), and the parental monitoring, substance use expectancies, and substance use reported by pre-adolescents. Family structure did not differentiate the substance use prevalence, expectancies or parental monitoring among the 1224 low-income, Mexican-origin fifth grade participants. Parents from all family types demonstrated similar levels of parental monitoring. More importantly, family composition was not related to pre-adolescents' substance use. Other analyses showed that the relationship between substance use and certain demographic variables (e.g. gender, country of birth, language use) did not differ across family structures. The report concludes by discussing possible developmental and resiliency factors in Mexican origin families that would account for these findings.