The present study was designed to determine bone density modifications at the forearm and metacarpal bones in patients with carpal tunnel syndrome (CTS). Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry at the one-third distal end and for the total of the radius-ulna, together with the third and fourth metacarpal bones, in 48 clinically and electrophysiologically diagnosed (18 unilateral and 15 bilateral) affected extremities in 33 premenopausal women (mean age 38.9 +/-6.5 years) with CTS. BMD values for non-affected extremities were used as controls for comparison with affected extremities. Bone mass was decreased approximately 7% in the forearm region (P<0.02) and 18% in metacarpal bones (P<0.01) of the thenar atrophy associated group compared with controls. A significant correlation was observed between disease duration (mean duration 3.2 +/-2.7 years) and the decrease in metacarpal bone density (r=0.43; P=0.004). This is the first clinical report of quantified bone loss in affected extremities in patients with CTS, and the results suggest the need for further studies to assess the clinical significance and morbidity of this pathology, especially in patients with thenar atrophy.