The advent of genomic and precision medicine has posed new challenges for neuroimaging and neurocognition. Instead of disjointed studies using single neuroimaging modalities and traditional paper-and-pencil neuropsychological testing, the field has been moving toward multimodal neuroimaging and computerized neurocognitive batteries that evaluate behavioral domains linked to regional brain anatomy and physiology. We describe an effort to ascend to this level of data acquisition and analysis by collecting the Philadelphia Neurodevelopmental Cohort (PNC), in which nearly 10,000 children age 8-21 were studied during 2009-2011 with a comprehensive battery of clinical and neurocognitive assessments and multimodal neuroimaging of 1,600 of these participants. We will describe the study and present initial results from analyzing these data to obtain information on the relationship between cognitive development and brain maturation. Thje analysis revealed marked sex differences in developmental trajectories.