The Koerber-Salus-Elschnig Sylvian aqueduct syndrome1 consists of the following findings: 1. Paresis of vertical gaze 2. Pupillary abnormalities 3. Tonic spasm of convergence on attempted upward gaze 4. Clonic convergence movements, or convergence nystagmus 5. Nystagmus retractorius 6. Vertical nystagmus on gaze up or down 7. Extraocular muscle pareses This is a report of two recently encountered cases of this rare entity in which nystagmus retractorius was associated with retraction of the upper lids. A unique optokinetic response, which to our knowledge has not been reported, was present in both patients. Report of Cases Case 1. —This 60-year-old white woman was seen through the courtesy of the neurology service at the Lemuel Shattuck Hospital. Except for asymptomatic hypertension for many years, she was in good health until Feb. 10, 1959, when she suddenly developed a headache at work and her eyes were noted to turn in. She rapidly became