A thorough knowledge of the functional vascular anatomy of the brain is becoming increasingly required in neuro-interventional procedures. Similarly, this knowledge is also required in neurosurgery, especially when a particular artery or vein is to be sacrificed during surgery. Permanent occlusion of a major artery can be challenged by a balloon occlusion test, but for venous sacrifice, such a procedure is practically not applicable. Up to now, reliable methods to judge the safety of such destructive procedures were lacking. Knowledge of the basic angioarchitecture of the cerebral veins, in other words, the “functional anatomy of the cerebral veins” may help us to better understand the safety or risk of sacrificing cerebral veins. Today, 3D-CT angiography, digital subtraction angiography and cone-beam CT provide detailed information on the precise cerebral venous anatomy to help us understand the functional venous anatomy and to make informed decisions.