This investigation examines the sociocultural influences on risk of first sex among a representative sample of Hispanic (primarily of Mexican origin) teens living in Los Angeles County. Teen acculturation (measured as language of interview) moderates the effects of gender on risk of sex, with less acculturated teens exhibiting the greatest gender difference. Teens living with both biological parents have significantly lower risk of sex and the effect of family acculturation (measured as generational status) operates through teens' language of interview. Neither measure of parent-youth relationship (socioemotional support, parental control) is significant. Hispanic teens living in low-density Hispanic neighborhoods have significantly higher risk of sex than do teens living in neighborhoods with higher levels of ambient hazards. The results highlight the importance of characterizing sociocultural influences at multiple levels of aggregation.