A study of spontaneous nystagmus in 121 normal subjects and 1601 patients suggests that an “idiopathic spontaneous nystagmus” is recorded with the subject's eyes closed in 20–25% of both the normal and patient population. This nystagmus is probably of no significance in the diagnosis of vertigo-producing disorders. It is of low intensity (usually below 6°/sec, but occasionally in the 6–10°/sec range), and is more frequently directed to the left than to the right. Spontaneous nystagmus above 10°/sec is of diagnostic significance. It is probable that such a nystagmus will be of peripheral origin and directed away from the side of the peripheral lesion.