• Magnetic resonance imaging in two children with idiopathic hypopituitarism demonstrated a signal of high intensity near the optic tract that was consistent with the signal produced by posterior pituitary tissue. Patient 1 was a 15-year-old girl with panhypopituitarism but intact posterior pituitary function. Computed tomography disclosed widening of the superior aspect of the pituitary stalk and a partially empty sella. Magnetic resonance imaging disclosed a 3-mm high-intensity signal abutting the optic tract in the midline just above the sella. The pituitary stalk was not clearly defined, the pituitary gland was small, and the sella was filled with cerebrospinal fluid. Patient 2 was a 12-year-old boy with isolated deficiency of growth hormone secretion. Findings from magnetic resonance imaging and computed tomography were similar to those in patient 1. These data suggest that the high-intensity magnetic resonance imaging findings represent a displaced or "ectopic" posterior pituitary gland, and that the hypopituitary state is due to an insult to the pituitary stalk.