✓ Delayed chiasmal syndromes after emptying of a Rathke's cleft cyst have not been reported previously. When these deficits occur following the treatment of parasellar lesions they are usually associated with the descent of a scarred optic system into an empty sella, and vision often improves promptly when the optic system is elevated. Two months after transsphenoidal surgery with emptying of a large intrasellar cyst, a 22-year-old man developed recurrent bitemporal visual field deficits over a 3-day period. Sagittal magnetic resonance images demonstrated an enhancing band of tissue extending anteriorly from the normally placed chiasm down to the anterior portion of the sella turcica. At craniotomy the enhancing tissue was found to be scar extending from the anterior border of the chiasm to the diaphragma sellae. The anterior portion of the diaphragm was resected as widely as possible without dissecting the scar itself from the chiasm. A membrane consistent with the wall of a Rathke's cleft cyst was found attached to the resected tissue. The patient's vision was improved 2 days after surgery. This case illustrates that traction by scar extending from the chiasm to the diaphragm, even when the chiasm is in its normal anatomical location, may cause progressive visual loss; and that untethering of the chiasm by resecting the diaphragm while leaving the scar intact can result in improved vision.