In 50 hospitalized patients with acquired immunodeficiency syndrome, signs of central eye movement limitation (28 cases) were most common. Peripheral eye movement limitations (18), abnormalities of vision (18), and abnormal spontaneous eye movements (15) occurred with about equal frequency. Meningitis (17), usually due to lymphoma (8) or Cryptococcus (8), was the usual cause of peripheral nervous system involvement, while toxoplasmosis (18) was more common than lymphoma (4) or presumed viral causes (8) in producing CNS dysfunction. The midbrain and pretectal (8) were affected about as often as the pontine tegmentum (9), but rostral brainstem lesions appeared to be the result of toxoplasmosis (4) or lymphoma (3), whereas a viral etiology was the presumed cause of most caudal stem involvement.