Neuroimaging studies have identified both macrostructural and microstructural evidence of white matter (WM) tissue maturation continuing through adolescence and into young adulthood. WM development is important for smooth and efficient communication between brain regions. Frontal WM association fibers are important pathways for higher order executive functioning (e.g., inhibition, attention, problem-solving), yet are slower to mature. The relationship between WM integrity and cognition is beginning to be explored in adolescence, with studies showing relationships between microstructural integrity and performance on tests of executive functioning such as response inhibition. Notably, adolescents are at increased risk for engaging in risky behaviors such as substance misuse and delinquency, yet limited studies have explored the relationship between WM changes and risk taking during adolescent development. Therefore, this study will utilize diffusion tensor imaging (DTI) to examine the influence of WM microstructural integrity and executive functioning on changes in real-word risk taking behaviors, including drug and alcohol use, measured over an 18-month interval during adolescence. If empirical support exists for structure-function associations such as WM integrity and risk taking, structural predictors can be used in accordance with other assessment tools (e.g., neuropsychological, personality, socio-cultural) and imaging modalities (FMRI) to better understand behavioral manifestation of real-world risk taking. Understanding the neural substrates of risky behaviors has implications for not only clinical assessment, but for designing intervention and prevention programs that take into account developmental differences in cognitive control capacities during the transitional window between childhood and adulthood. Such information may be used to provide healthier outlets for teenagers, which could influence healthcare, education, criminal justice systems, and society as a whole.