The brain is an immune privileged organ due to the presence of a blood-brain barrier and the lack of lymphatic vessels within the CNS parenchyma. However, it has been clear for several decades that CNS antigens drain into regional lymph nodes. In humans, soluble amyloidβ is produced by neurons and is deposited in the walls of ageing cerebral blood vessels as cerebral amyloid angiopathy (CAA), providing thus a natural tracer for the drainage of solutes. Our anatomical experimental studies using wild-type mice demonstrate that injection of soluble tracers in the gray matter of the brain results in diffusion and drainage of the tracers along the basement membranes of capillaries and the basement membranes surrounding smooth muscle cells of arteries, towards the surface of the brain. This pathway is effectively the lymphatic drainage pathway of the brain and is restricted to solutes, as nanoparticles of 15nm cannot enter the cerebrovascular basement membranes. Ageing, possession of apolipoprotein E4 and vascular immune complexes block this drainage pathway, resulting in CAA. The cerebrovascular basement membranes are also the pathway for convective influx of cerebrospinal fluid (CSF) into the brain. Specifically, the glial-pial basement membranes are the pathways for convective influx of CSF. Using optimally preserved canine brain tissue we have demonstrated that the structure of the wall of arteries is different in gray matter compared to white matter, providing thus a platform for better interpretation of age-related white matter hyperintensities. Our results clarify the exact pathways for lymphatic drainage of the brain parenchyma and for convective influx of cerebrospinal fluid.