A total 5,600 cGy in 28 fractions in 44 days was delivered to a 53-year-old woman with acromegaly after transsphenoid removal of a pituitary adenoma. Sixteen months later, she suffered a progressive loss of vision. Radiation optic neuropathy was diagnosed. A T1-weighted imaging showed gadolinium-enhanced lesions in the optic chiasm, pituitary stalk and hypothalamus. Magnetic resonance imaging is uniquely suited to detect radiation injury to the sellar region. The complications of radiation therapy for benign tumor can be severe even by current standard procedures.