Twenty asymptomatic volunteers (mean age 33 years, range 26 - 54 years) underwent investigation using duplex Doppler ultrasound with real-time imaging and colour flow enhancement. With the subjects seated, peak velocity at C1-2 and volume flow rate at C5-6 were measured in the artery contralateral to the direction of rotation, in the four positions of neutral, 45 degrees and end range rotation, plus a subsequent neutral position. No change in peak velocity at C1-2 between the initial neutral measurement and the measurements at 45 degrees and end range rotation was found (P>0.05). Peak velocity was less in both vertebral arteries on return to the neutral position as compared with end range rotation, however the difference was significant for the left vertebral artery only (P=0.005). This lends support for the rest period, which is taken between cervical movement tests when conducting pre-manipulative testing, to allow for any latent effect on blood flow of the tests themselves. There was no change in volume flow rate between any of the test positions (P=0.349). There was no indication of a cumulative effect of the test procedure (P>0.05).