Computed tomography analysis was conducted in 29 patients with 34 carpal canal syndromes to determine structural modifications of the wrist during the immediate preoperative period and two and three months after operation. The carpus was analyzed at 3 levels of the section: proximal at the entrance orifice of the canal, median and distal at the orifice of exit, with the wrist at rest and then in maximum active flexion and extension. Results showed that the increase of canal caliber (and therefore the decrease in local increase in pressure) continued during the second and third postoperative months, at rest as well as in flexion or extension. It appears, further, that opening of the canal does not alter structural organization of wrist bones or ligaments, the increases in caliber obtained varying in the same sense whatever the position of the wrist or the level of the section.