Eighteen patients with congenital nystagmus were studied with the techniques of electronystagmography and computer analysis. We found several complex waveforms of congenital nystagmus in the primary position of gaze above those of jerk and pendular nystagmus as defined clinically. An etiologic classification of motor fixation defect and sensory fixation defect nystagmus based on waveforms is not justified. Ocular tracking studies demonstrate that the smooth pursuit system is operational in congenital nystagmus and substantiate the belief that the fast component of jerk nystagmus is a corrective movement generated by the saccadic system. Patients with congenital nystagmus are able to produce voluntary saccades with normal velocity-amplitude relationships.