Currently, the hypothesis that altered venous hemodynamics might play a causative role in the pathogenesis of multiple sclerosis (MS) is being controversially discussed. This new "venous hypothesis" postulates that obstructions of the cervical venous system cause an increased pressure of the intracranial venous system and that in turn intracranial congestion disintegrates the blood-brain barrier initiating the inflammatory process in MS.The "venous hypothesis" is analyzed and evaluated with regard to the following aspects: first concerning the validity of published data, second with regard to the plausibility in view of the currently approved pathogenetic model of MS, and third with regard to the compatibility with preliminary neurosonological findings in a small but unselected cohort of patients at our department.The authors conclude that the "chronic cerebrospinal venous insufficiency (CCSVI)" cannot represent the exclusive pathogenetic factor in the pathogenesis of MS. In our cohort, only 20% of the patients fulfilled the required neurosonological features of CCSVI. So far, the pathogenetic relevance of these findings remains speculative. Thus, based on the current scientific position we cannot justify invasive "therapeutic" approaches, especially if they are performed outside of clinical trials.