The modified Camitz procedure has been used to improve thumb opposition in patients with severe carpal tunnel syndrome (CTS), although its indications remain controversial. This study compared the functional recovery of thumb opposition following carpal tunnel release with and without a concomitant Camitz procedure. We used the Carpal Tunnel Syndrome Instrument questionnaire (CTSI) and the compound muscle action potential of the abductor pollicis brevis (APB-CMAP) to assess the recovery. Five hundred sixty-seven hands underwent surgical treatment for CTS following electrophysiologic studies and the CTSI. The procedures included carpal tunnel release (either endoscopic carpal tunnel release [ECTR] or open carpal tunnel release [OCTR]) and OCTR with a Camitz procedure. One hundred thirty-six patients with absent preoperative APB-CMAP constituted the material of our study. The CTSI and APB-CMAP recoveries between the "ECTR/OCTR group" and the "Camitz group" were compared before surgery and at three, six, and 12 months after surgery. There were no statistically significant differences in recovery between the "ECTR/OCTR group" and the "Camitz group" according to the three scales of CTSI (symptom severity scale, functional state scale, and FS-2 item, buttoning clothes: an alternative test of thumb opposition) and the APB-CMAP. Carpal tunnel release procedures resulted in the useful recovery of thumb opposition without the need for Camitz, even if APB-CMAP did not fully recover. The action of the other synergistic muscles acting on the thumb and the sensory recovery may have contributed to the recovery of thumb opposition. The Camitz procedure also may be only rarely indicated for hands affected by severe CTS. Therapeutic IV.