Background Transitions into heavy alcohol use often already take place during adolescence and are likely to be both genetically and environmentally determined. Therefore, in a 6-wave longitudinal study, we examined the effects of DRD2 Taq1A and OPRM1 A118G genotypes and the interaction with parental rule-setting on different groups of adolescent drinkers. Methods Growth mixture modeling resulted in 3 distinct groups of adolescent drinkers: light drinkers (n=346), moderate drinkers (n=178), and heavy drinkers (n=72). Results Multinomial regression showed that moderate drinkers carried the OPRM1 G allele and received lower levels of parental rule-setting significantly more often than the light drinking group. No other significant main effects of DRD2, OPRM1, and rule-setting were found. The interaction between OPRM1 genotype and parental rule-setting significantly distinguished the heavy drinkers from the light (p