In man, as has been shown previously in rabbits and monkeys, a nystagmus can be elicited by monocular intermittent photic stimulation. The direction of nystagmus (FIN) is always towards the stimulated eye. This nystagmus strongly resembles latent nystagmus. Here the fast phase is always directed towards the 'non-occluded' eye. The FIN may, therefore, be used as a model for the study of mechanisms underlying these pathological conditions. For further elucidation of FIN, studies were made in rabbits.