Whiplash injury is not only limited to neck injury but also brainstem injury that does not involve direct damage to the neck or head. The symptoms of whiplash injury are polymorphous, with the most common complaints being cervical pain, headache and scapulodynia. Vertigo and dizziness are also reported in 25-50% of the cases. In otoneurologic studies, magnetic resonance angiography (MRA) is used for the evaluation of vertebrobasilar hemodynamics in patients who complain of dizziness and vertigo. It is reported that vertebrobasilar artery insufficiency (VBI) leads to brainstem and cerebellar ischemia and infarction following cervical manipulation. Here we examined the correlation between vertigo or dizziness and the right and left side difference in vertebral arteries after whiplash injury using MRA. We studied 20 patients who complained of neck pain with vertigo or dizziness after whiplash injury and 13 healthy volunteers as a control. In the control group, abnormal MRA findings in the vertebral arteries such as occlusion, stenosis or slow blood flow were seen in 77% of the cases. In the patient group, abnormal MRA findings were seen in 60%. The side difference in blood flow was 3.5+/-2.5 cm/s in the control group and 6.1+/-3.0 cm/s in the patient group. Our findings suggest that some subjects with persistent vertigo or dizziness after whiplash injury are more likely to have VBI on MRA. VBI might be an important background factor to evoke cervical vertigo or dizziness after whiplash injury. The side difference between the two vertebral arteries could cause a circulation disorder in the vertebrobasilar system after whiplash injury. However, the VBI on MRA itself was also seen in the control group, and thus it is not clear whether it is due to whiplash injury in the patient group.