Clearance of waste products from the brain is of vital importance. Recent publications suggest a potential clearance mechanism via paravascular channels around blood vessels. However, the anatomy, driving forces, and flow pattern into and out of the brain along these channels remain poorly characterized. In this study, we directly observed paravascular flow through a thinned-skull cranial window in anesthetized mice (ketamine 75 mg/kg, dexmedetomidine 0,5 mg/kg). In this model, we observed that microspheres moved preferentially in the paravascular space of arteries rather than in the adjacent subarachnoid space or around veins. Paravascular flow was pulsatile, generated by the cardiac cycle, with net antegrade flow along leptomeningeal arteries. Confocal imaging confirmed that microspheres distributed along these arteries, while their presence along penetrating arteries was limited to few vessels. Smaller tracers (4 kD and 500 kD) injected into the CSF of mice and rats revealed paravascular spaces around arteries that penetrated the brain and mostly followed the cisterns and clefts between brain territories. Tracers injected directly into the hippocampus dispersed inhomogeneous, with accumulation at border zones between brain parenchyma and cerebrospinal fluid, and accumulation and spreading along arteries. This suggests that interstitial fluid drains into the CSF while larger solutes are retained by sieving. Distribution of tracers was drastically enhanced in spontaneously hypertensive rats, but removal from the brain was not affected. Collectively, these data suggest that paravascular spaces around leptomeningeal arteries form low resistance pathways on the surface of the brain that facilitate cerebrospinal fluid flow. Much more narrow paravascular spaces exist around arteries that penetrate the brain. Most likely, arterial pulsations induce mixing of the fluid in these spaces. This facilitates exchange between the interstitial fluid and CSF, and thereby aids the removal of waste products from the brain.