A patient with unusual bilateral papilledema and exudative retinopathy was found to have a histologically-proven hamartoma which apparently arose from the region of the hypothalamus. He was an adult in otherwise good general health. There was no history of precocious puberty or abnormal body growth during adolescence, which is unusual in patients having this lesion. To our knowledge this is the first case in which ophthalmoscopic and visual field changes have been noted. The presenting symptom was decreased vision. Hamartomas are lesions that lie in a "twilight zone" between obvious developmental defects and benign tumors. The derivation of the term "hamartoma" comes from the Greek "hamarto" meaning to fail, plus "-oma" meaning tumor. A hamartoma is defined as a nodular or tumor-like mass resulting from faulty embryonal development of the cells and tissues normally found in that area.1,2,3 The tumor is congenital. It is present at birth and has