The objective of this chapter is to introduce the ventricles of brain. The cavities of brain are called ventricles. There are four ventricles in brain such as right and left lateral ventricles, third ventricle, and fourth ventricle. This chapter covers the circulation of cerebrospinal fluid, lateral ventricle, third ventricle, circumventricular organs, fourth ventricle, and subarachnoid cisterns. Lateral ventricle is the cavity of telencephalon or cerebrum. Third ventricle is the cavity of diencephalon part of brain. Superiorly communicates with lateral ventricles through interventricular foramen of Monro on either side. Fourth ventricle is the cavity of rhombencephalon. It is also called as rhomboid fossa.