The scapholunate interosseous ligament, which connects the carpal scaphoid and lunate bones, was evaluated by gross dissection and serial histologic sections in transverse, sagittal, and coronal planes in 21 fresh and 16 fixed adult cadaver wrists. The scapholunate interosseous ligament is consistently divisible into three anatomic regions: dorsal, proximal, and palmar. The dorsal region is thick and composed of short, transversely oriented collagen fibers. The proximal region is principally composed of fibrocartilage, with a few superficial, longitudinally oriented collagen fibers. The proximal region may extend distally a few millimeters into the scapholunate joint space, thus resembling a knee meniscus. The radioscapholunate ligament separates the proximal and palmar regions of the scapholunate interosseous ligament, often extending distally to cover the dorsal surface of the palmar region of the scapholunate interosseous ligament. The palmar region is thin and composed of obliquely oriented collagen fascicles, just dorsal to and separate from the long radiolunate ligament.