The main objective of this research was to analyze the influence and the differential weight of certain family factors in Spanish adolescent substance abuse. A representative sample of 1,680 students of both sexes from all over Spain took part in the study. The results show that the variables associated with drug consumption are: male, one-parent-family background, family conflict, poor parent-child relationships, few shared activities, permissive parenting style, permissive attitudes to drugs in the family, and parents' drug consumption. Moreover, risk factors specific to drugs have greater influence than general risk factors. These results have very important implications for the design of family drug-prevention programs in Spain.