Summary Bone density was studied in ten patients before and after release of an idiopathic carpal tunnel syndrome. A corticomedullary ratio was measured at the mid-point of the metacarpals and proximal phalanges of both hands. There was a significant increase in the mean bone density over the period of observation in the thumb and middle finger metacarpals and in the index, middle, and ring finger proximal phalanges of the operated hand. The was no significant increase in the density of either metacarpal or proximal phalanx on the non-operated side. Release of the carpal tunnel syndrome provides not only symptomatic relief but also leads to increased bone density.