Morphometric measurements of the carpal bones were carried out in 32 patients with carpal tunnel syndrome (CTS) and in 47 normal persons, using high resolution CT. Measurements of distances and areas were carried out at the entry of each carpal tunnel and at its narrowest point. In idiopathic CTS there were no significant differences in these measurements from normal carpal measurements. The situation was different in ten patients with nonidiopathic CTS; in these CT showed the cause of median compression reliably. Our results suggest that there are no indications for performing CT of the wrist in idiopathic CTS, but that valuable information may be expected from CT in cases of nonidiopathic CTS.