Consistent with Moffitt's theory, the results of the analyses revealed that the maturity gap was predictive of minor forms of delinquency and drug use but not of more serious types of offending behaviors for males. The findings were less supportive of Moffitt's hypothesis for females. Moffitt's maturity gap thesis is a viable explanation of adolescent delinquency, especially for males. This portion of the theory, which has largely gone unexamined, warrants further inquiry from criminologists. The purpose of this study was to provide the first direct test of Moffitt's (1993) hypothesis linking the maturity gap with adolescent delinquency. Data were drawn from the National Longitudinal Study of Adolescent Health (Add Health) and a direct measure of the maturity gap was constructed. Tables, figure, appendix, notes, and references