The currently advocated pre-manipulative risk assessment protocols include the use of provocative positional tests to challenge the integrity of the vascular supply to the brain. This paper examines the validity of these pre-manipulative provocative tests in light of recent studies involving ultrasound scanning of the vertebral arteries in subjects who also had provocative tests performed. These studies indicate that the provocative positional tests may produce both false positive and false negative findings. Recent research concerning the use of a continuous wave Doppler velocimeter suggests this device may provide a more objective assessment of vertebral artery blood flow than the present provocative tests. However, the sensitivity and specificity of the use of the velocimeter in identifying altered or abnormal vascular flow in the vertebral arteries, and therefore its clinical utility, remain to be fully established.