Over a 23-month period, 25 patients aged 11 to 74 years presented to our Level I trauma center with odontoid lateral mass asymmetry of 2 to 5 mm on properly centered AP open-mouth X-rays: 32% of patients were asymptomatic, 68% had cervical pain, and 32% had limited range of motion. Patients with cervical spine fractures or dislocations and those with fixed deformity were excluded. The clinical significance of asymmetry was determined utilizing dynamic axial CT scanning of the occiput (C0), atlas (C1) and axis (C2) with the head neutral and with 15 degrees to 30 degrees active rotation. Nineteen patients demonstrated greater than 5 degrees of relative motion of C1 on C2 bilaterally. Three patients had less than 5 degrees of relative motion bilaterally and three patients had less than 5 degrees relative motion with left rotation only. No patient had formal treatment and all had nearly normal cervical range of motion on clinical examination at the time of hospital discharge. The finding of an asymmetric odontoid-lateral mass interspace on properly centered open-mouth AP X-rays in the presence of otherwise normal cervical spine X-rays, in conscious patients without fixed deformity, appears to be incidental and requires no further evaluation or treatment.