The scaphotrapeziotrapezoidal (STT) joint is a complex joint in which the arthroscope and instruments can be used through the radial midcarpal and STT-ulnar portals. This report describes a new arthroscopic portal at the STT joint to complete and improve the evaluation and treatment of this joint by arthroscopy: The STT-radial (STT-R) portal is situated immediately radial to the abductor pollicis longus at the STT level. Five cadaveric wrist specimens were dissected immediately after the portal was established, and photographed to determine the proximity of neurovascular structures. Magnetic resonance imaging evaluation of 15 hands was performed to measure the proximity of the radial artery. A cadaveric distal scaphoid excision was also created arthroscopically to show the real usefulness of this portal. Results of the anatomic study showed that no lesions of nerves or vessels were seen at this portal. Magnetic resonance imaging showed that the radial artery was located at a safe distance from the portal. The distal scaphoid excision was performed 15 minutes after the STT portals were established. Our results suggest that this new portal is safe and effective.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 5 (May-June), 2003: pp 547–553