Results of this paper suggest that influential others, including siblings and cousins, should be included in measures of family structure, as they had significant associations with drug use in the work presented. Also noted were various study limitations. The work states that the findings have implications for the way in which family structure is assessed, and for the development of family-focused interventions to prevent adolescent drug use, as family structure is one factor that can help explain drug use among adolescents. The data was a result of a 2005 study conducted with 255 ninth-grade students from an urban, predominantly Latino Los Angeles area high school. Students were 83 percent Latino, 58 percent female, and from mostly low socioeconomic status (SES) households. Half of all students reported having ever used alcohol, 30 percent had ever smoked a cigarette, and 18 percent had ever used marijuana. Family structure was measured using a single open-ended question and logistic regression was employed to determine the effects of various family structures on the use of alcohol, cigarettes, and marijuana. The presence of older siblings in the home was associated with alcohol and marijuana use, and living with a cousin was associated with marijuana use. Tables, references