Thirty-four patients who had fractures of the atlas (the first cervical vertebra) were reviewed at an average follow-up of 4.5 years. Seventeen patients had bilateral fracture of the posterior arch of the first cervical vertebra. Eight were treated with immobilization in a cervical orthosis, with no long-term problems secondary to the injury. Nine of these patients had additional fractures in the first and second cervical vertebral complex, complicating the management of the fractures of the posterior arch. Two of the nine patients died, and the treatment of the other seven was dependent on the additional fractures. A second group of six patients had a fracture in the area of the lateral mass, with one fracture just anterior to or within the anterior portion of the lateral mass of the first cervical vertebra and a second fracture posterior to the lateral mass of the first cervical vertebra on the same side; resultant asymmetrical displacement of the lateral masses was seen on the open-mouth roentgenogram that was made for each patient. A third group of eleven patients sustained a Jefferson, or burst, fracture of the first cervical vertebra. These patients had either four fractures (two in the anterior arch and two in the posterior arch) or three fractures (one in the anterior arch and two in the posterior arch). Spreading of the lateral masses was relatively symmetrical on the open-mouth roentgenogram. Patients who had fractures with displacement of two to seven millimeters were treated with immobilization in a halo vest. Patients who had fractures with severe spreading of the lateral masses (more than seven millimeters) were treated with reduction of the lateral masses by axial traction until healing of the arch had occurred. No atlanto-axial instability was evident in any patient at follow-up.