• Flash-evoked visual responses of two patients from a family with congenital nystagmus showed marked asymmetry between the recordings from the right and left occipital regions in response to monocular stimulation. The asymmetries were crossed, ie, the degree of abnormality inverted when the stimulus changed from one eye to the other. Stimulation of both eyes together evoked symmetrical responses from the two hemispheres. The patients had no signs of abnormality involving the visual pathways. The changes in the visually evoked responses were similar to those found in human albinos, who are known to have abnormal retinostriate projections and also nystagmus.