Erdheim-Chester disease (ECD) is a rare multiple system histiocytosis that is characterized pathologically by xanthogranulomatous infiltrates and radiologically by symmetrical sclerosis of long bones. The diagnosis is often confirmed by biopsy of bone or of orbital or retroperitoneal soft tissue. Intracranial involvement is rare. The authors report a case of ECD in which the diagnosis was made after biopsy of a hypothalamic mass. The mass had been discovered during a workup for panhypopituitarism in a 55-year-old man with urological and bone disease. Aside from diabetes insipidus, other features of pituitary insufficiency have seldom been reported and no patients have presented with a hypothalamic tumor. The endocrinological and neurological aspects of ECD are discussed, as is its differential diagnosis. Reported cases of the disorder associated with hypopituitarism or found during biopsy of central nervous system structures are also reviewed.