In this case discussion from Neuro-Ophthalmology Subspecialty Day 2011, a patient suspected of a microvascular third nerve palsy displays incomplete lowering of the eyelid on infraduction and elevation of the eyelid on adduction, both signs of aberrant regeneration of the third cranial nerve. Aberrant regeneration of the third ocular nerve is a key “red flag” in neuro-ophthalmology that indicates, in the absence of a history of trauma, that the palsy is due to a more serious underlying lesion such as an aneurysm or tumor.