See-saw nystagmus is an extreme rarity, first reported by E. E. Maddox1 in 1914. In this phenomenon, the movements of the two eyes are pendular and dissociated, one rising while the other falls in opposite directions resembling a see-saw. Maddox' case was a 53-year-old man with a bitemporal hemianopia. We are aware of but one other reported case.2 In the latter, see-saw nystagmus was noted in a patient with extremely low vision attributed to toxoplasma chorioretinitis. The following is the third reported case, and the first case of see-saw nystagmus with histologic verification. Report of a Case A 10-year-old white girl was first admitted to the Massachusetts General Hospital on Nov. 10, 1958. The chief complaint was "twitching eyes" of five months' duration. The girl had enjoyed excellent health until June, 1958, when one day a friend happened to notice that the patient's eyes were "twitching." Three months