Background and purpose: Multiple sclerosis (MS) is a chronic inflammatory disease of central nervous system. We aimed to investigate the cerebral blood flow velocity (CBFV) changes in MS by transcranial Doppler. Methods: Twenty patients with MS, 20 age-matched healthy controls were included in the study. In both groups, blood flow velocities (BFVs) of middle cerebral arteries (MCAs) were evaluated. The changes of blood pressure, heart rate along with the changes in BFV of MCA were recorded after the patients were raised to upright position. Results: In both groups, upon raising the tilt table to the upright position, the mean CBFV values were found to be lower in comparison with the recorded baseline values (P values < 0.05). The decline in the mean CBFV values was more significant in patients with MS (P = 0.01). Conclusion: Our study showed upon raise of the tilt table, the mean BFVs decreased more in MS patients than control group with a more prominent change in the subgroup of MS patients with expanded disability scale scores >= 2. By use of transcranial Doppler ultrasound, it may be possible to evaluate BFV changes in patients with MS.