It is only recently that the use of the endoscope as the sole visualizing tool has been introduced in transsphenoidal pituitary surgery with its favorable related implications and minimal operative trauma. Of course, microscopic and endoscopic anatomy are basically the same, but the optical distorsion of endoscopic images is quite substantial compared to microscopic depictions. An endoscope lens produces images with maximal magnification at its center and severe contraction at its periphery. Nearer images are disproportionally enlarged and remote images are falsely miniaturized. This optical illusion may disorientate a surgeon who is not familiar with this peculiar condition at the skull base. This atlas acts as a guide through the endoscopic anatomy and gives detailed descriptions of the preoperative management and the surgical procedures.