Identification of the cause of a patient's nystagmus requires a systematic and complete ocular motor evaluation. Clinical findings and the features of nystagmus will be used to identify the underlying abnormality.Both a diagnostic approach and the pathophysiologic mechanism as well as the therapy will be tackeled. Latent nystagmus, manifest latent -, congenital -, monocular -, gaze evoked -, periodic alternating-, see-saw-, vestibular-nystagmus, square wave jerks, ocular flutter and opsoclonus will be discussed.