Objective: To determine if chronic cerebral venous insufficiency exists in patients with multiple sclerosis (MS) using ultrasonography and 4-dimensional color Doppler ultrasonography examination and unverified criteria proposed by Zamboni et al. Design: Patients with MS and clinically isolated syndrome were matched by age and sex with subjects with migraine or no neurological disease. All subjects underwent gray-scale, color, and spectral Doppler ultrasonography examination of the internal jugular veins (IJVs), vertebral veins, and deep cerebral veins for stenosis, absence of signal, and reflux. Setting: Academic MS center. Patients: All patients with MS fulfilled revised McDonald criteria for the diagnosis of MS. Patients with clinically isolated syndrome exhibited a typical transient focal neurological deficit and had magnetic resonance imaging lesions typical of MS. Control subjects were recruited from the VA migraine clinic or staff. Main Outcome Measures: Five parameters of venous outflow used by Zamboni et al. were examined: (1) IJV or vertebral vein reflux, (2) deep cerebral vein reflux, (3) IJV stenosis, (4) absence of flow in IJVs or vertebral veins, and (5) change in cross-sectional area of the IJV with postural change. Results: There was no significant difference in the number and type of venous outflow abnormalities in patients with MS compared with controls. Conclusion: This study does not support the theory that chronic cerebral venous insufficiency exists in MS.