Nine cases of unstable Jefferson variant atlas fractures were treated with nonoperative external immobilization between 1989 and 1993. All of them were studied by plain films and CT scans. Seven cases had three breaks of the atlas ring. One case had unilateral anterior arch fracture, associated transverse ligament tear and quadriplegia. The other case had Jefferson, Hangman, C3pedicle burst fractures and C3,4dislocation. All of the fractures were unstable or potentially unstable. Despite the abnormal open month view in all cases, the plain films showed minimal abnormalities, requiring CT for definite diagnosis. Follow-up for average of 16 months showed the 7 cases showed the fractures healed with good bone bunion, complete mobility and no residual pain.