The Aging, Dementia and Traumatic Brain Injury Study is a detailed neuropathologic, molecular and transcriptomic characterization of brains of control and TBI exposure cases from a unique aged population-based cohort from the Adult Changes in Thought (ACT) study. This study was developed by a consortium consisting of the University of Washington, Kaiser Permanente Washington Health Research Institute, and the Allen Institute for Brain Science, and was supported by the Paul G. Allen Family Foundation. This freely available resource (http://aging.brain-map.org/) presents a systematic and extensive data set of study participant metadata, quantitative histology and protein measurements of neuropathology, and RNA sequencing (RNA-seq) analysis of hippocampus and neocortex. Specific methodological details are available on the “Documentation” tab at http://aging.brain-map.org/. Included in this data set are normalized RNA-Seq FPKM files used for analysis in "Neuropathological and transcriptomic characteristics of the aged brain", published in eLife. Other processed data files as well as sample and donor meta-data and QC metrics are available at http://aging.brain-map.org/download/index Controlled access to raw data files is available via https://www.niagads.org/datasets/ng00059 Overall design: In total, 376 samples collected from cortical grey (parietal and temporal) and white matter (parietal) and hippocampus from a total of 107 brains are presented in this resource (one of the 377 samples from the original resource was not included in analyses for the manuscript). This study includes 55 participants of the ACT study self-reporting TBI with loss of consciousness, along with 55 individuals matched for age, sex, and year of death who did not report a TBI with loss of consciousness (three donors were removed as outliers prior to performing the analysis).