We describe the occurrence of a supracellar ectopic pituitary adenoma in a 34 year old woman who presented with cranial diabetes insipidus and subsequently developed galactorrhoea-amenorrhoea. The tumour was demonstrated by both contrast computed tomography scan and magnetic resonance imaging with gadolinium enhancement and was confirmed at operation. Histological examination showed that the suprasellar lesion consisted of a pituitary adenoma while the pituitary biopsy revealed an unrelated pituitary microadenoma embedded in normal pituitary tissues. A review is made of the reported cases of ectopic pituitary adenomas.