We reported previously that intravenous infusion of atriopeptin increases blood flow to the choroid plexus. The first goal of this study was to determine whether blood-borne atriopeptin increases the production of CSF. Ventriculocisternal perfusion was used to measure the production of CSF in anesthetized rabbits. Atriopeptin increased blood flow to the choroid plexus (measured with microspheres) but did not alter the production of CSF. The second goal of the study was to determine whether intracerebroventricular injection of atriopeptin affects the production of CSF. Injection of atriopeptin into the cerebral ventricles increased blood flow to the choroid plexus but produced a small decrease in production of CSF. In summary, blood-borne and intraventricular atriopeptin increase blood flow to the choroid plexus, but do not increase the production of CSF.