We present a case of growth hormone (GH)-secreting ectopic pituitary adenoma confined to the sphenoid sinus associated with a normal-sized empty sella. It has been well known that acromegaly is sometimes associated with an empty sella. However, such a case usually has a macroadenoma and an empty sella that is large. The authors considered the possible mechanisms of the association between a normal-sized empty sella and an ectopic pituitary adenoma in the sphenoid sinus as the following. Primary empty sella existed originally, and the pituitary adenoma developed later. The adenoma extended into the sphenoid sinus because of the pulsatile intracranial cerebrospinal fluid pressure. Copyright 2002, Elsevier Science Ltd. All rights reserved.