Published in Psychiatry Research, the following longitudinal study investigates pre-post changes in brain gray matter concentration attributable to participation in a Mindfulness-Based Stress Reduction (MBSR) program. Anatomical MRI images from sixteen healthy, meditation-naïve participants were obtained before and after they underwent the eight-week program. Changes in gray matter concentration were investigated using voxel-based morphometry, and compared to a wait-list control group of 17 individuals. Results confirmed increases in gray matter concentration within the left hippocampus in the MBSR group compared to the controls. The results suggest that participation in MBSR is associated with changes in gray matter concentration in brain regions involved in learning and memory processes, emotion regulation, self-referential processing, and perspective taking.