The hypophysis cerebri, or pituitary gland, is a complex neuroendocrine organ involved in the control of a variety of homeostatic mechanisms. Subtleties in the internal anatomy of this gland are now becoming appreciated, such as the topographic arrangements of pituitary cell types and specializations in its regional microcirculation. A large number of potential lesions may affect the pituitary, including tumors (adenomas, Rathke cleft cysts, and craniopharyngiomas), inflammatory processes (adenohypophysitis, infections), and vascular lesions (apoplexy, infarction). Diseases isolated to the posterior lobe and stalk (eg, pituitary dwarfism, choristoma, diabetes insipidus) are also well recognized. Modern radiologic techniques like computed tomography (CT) and magnetic resonance (MR) imaging have provided new insights into the morphologic changes of the gland that occur both in health and in a variety of diseases. The picture of the gland that has emerged from this research is a dynamic one: The pituitary undergoes dramatic changes in size and shape throughout life that must be recognized when assessing it for pathologic change.