1. The arterial supply and the venous drainage of the human pituitary body have been studied in preparations injected with neoprene latex or Berlin blue.2. The pituitary body receives its arterial blood from the internal carotid arteries through a superior and an inferior hypophysial artery on either side.3. Each superior hypophysial artery distributes branches to the hypophysial stalk and gives off a substantial branch, the artery of the trabecula, which courses through the pars distalis and eventually supplies part of the lower infundibular stem. Each inferior hypophysial artery divides into a medial and a lateral branch. These branches anastomose with the corresponding vessels of the opposite side, forming an arterial ring around the neural lobe. Branches springing from this arterial ring supply the neural lobe and part of the lower infundibular stem.4. Interarterial anastomoses are a characteristic feature of the vascular arrangements of the human pituitary body. Branches of both the superior and the inferior hypophysial arterial systems anastomose freely with other branches of the same system. In addition, anastomoses of large calibre are present which connect branches of one of these two arterial systems with branches of the other.5. No branches of either the superior or the inferior hypophysial arteries supply the epithelial tissue of the pars distalis.