Magnetic resonance angiography (MRA) is an accurate non-invasive tool for imaging the cerebral vessels. It provides morphologic information about the cerebral vessels relying on blood flow as the physical basis for generating contrast between stationary tissues and moving spins. 'Selective' MRA gives functional information about the cerebrovascular system such as flow direction, origin of flow, and presence or absence of collaterals. Arteries and veins can be imaged selectively due to their usually opposite flow directions. Although at a relatively early stage of development, MRA has already become a widely used tool for the study of the cerebrovascular system.