Adolescence is a period of development characterised by risk taking typically involving the initiation and escalation of alcohol and drug use. Adolescence is also a critical period of neurobiological change behaviourally manifested as increases in impulsivity. Contemporary models of personality conceptualise impulsivity as a trait with at least two related but distinct factors (reward drive and rash impulsivity). Both are said to play a role in the propensity to engage in substance use and the escalation of alcohol and drug use. This model assumes that personality influences substance use however it is also possible that substance use may influence the development of personality. The current study investigated the cross-sectional and prospective bi-directional relationships between reward drive and rash impulsivity, and alcohol use and substance use problems in males and females. A prospective longitudinal design was used involving 1059 adolescents (males = 526, females = 533) followed up annually for 5 years from Grade 8 to Grade 12. Using , the results of this research provided support for a two-factor model of impulsivity. Further, evidence was found for bi-directional relationships between personality and substance use. As expected, the bi-directional relationship between initial levels of reward drive and rash impulsivity were significantly associated with initial levels of alcohol use and substance use problems. Rash impulsivity at baseline was a significant predictor of growth in alcohol use for both males and females. There was a significant association in the bi-directional relationship between growth in reward drive and rash impulsivity, and growth in alcohol use and substance use problems. The results of a sequential LGM found that escalated substance use problems overtime increased reward drive and rash impulsivity overtime for females only. The results of this study show that reward drive and rash impulsivity both contribute differentially to the escalation of substance use. Further, the converse of this relationship was also found where substance use influenced personality development. These findings highlight several risks for adolescents during critical periods of development and suggest the importance of early detection and interventions for at risk adolescents.