Attitudes to institutional authority, strength of support for moral values and maturity of socio-moral reasoning have all been identified as potential predictors of adolescent delinquency. In a sample of 12-15-year-old boys (N = 789), after checking for effects of age, IQ, social background and ethnicity, self-reported delinquency was significantly and independently predicted by attitudes to authority (r= -0.47) and moral values (r = -0.27), but not by a structural measure of moral reasoning level (r = -0.04). The findings argue for closer attention to the developmental determinants of attitudes to institutional authority and strength of moral value commitments than these have received hitherto. On the other hand, lack of an association between moral reasoning level and delinquent conduct does leave unanswered questions about the consequences of this kind of moral competence.