Congenital nystagmus (CN) is a common disorder indicative of a primary disturbance of the ocular motor or visual sensory systems. The authors prospectively evaluated 81 patients with CN, structurally normal eyes, and minimal or no abnormalities of the optic nerve, macula, and retinal pigment epithelium (RPE). Seventy-four (91%) patients were found to have a disorder of the visual sensory system. Thirty-four patients had albinism, 37 had a congenital or early onset disorder of the retinal photoreceptors, and 3 had abnormalities of the optic nerve. The remaining seven (9%) patients had motor CN. Most patients presenting with CN have visual loss and should be evaluated for an underlying disorder of the visual sensory system.