Spontaneous nystagmus was examined each eight hours after secondary endolymphatic sac immune response. Spontaneous nystagmus was seen in 13 of 19 animals. Direction of nystagmus was contralateral unchallenged side (left). Nystagmus appeared within 3 days. Duration of nystagmus was from 1 day to 4 days. Spontaneous nystagmus was found in all animals of which caloric responses resulted in afunction.