Musicians learn complex motor and auditory skills at an early age and practice these specialized skills extensively from childhood through their entire careers. Using a voxel-by-voxel morphometric technique, we found gray matter volume differences in motor as well as auditory and visuospatial brain regions comparing professional musicians (keyboard players) with matched amateur musicians and nonmusicians. These multiregional differences might represent structural adaptations in response to long-term skill learning and repetitive rehearsal of these skills. This is supported by finding a strong association between structural differences, musician status, and practice intensity as well as by a wealth of supporting animal data showing structural changes in response to long-term motor training.