Abnormal decussation of temporal retinogeniculostriate projections associated with albinism is reflected in the potential distribution of the visual evoked potential (VEP). Following monocular stimulation misrouted optic pathway projections produce VEP asymmetry across the occipital left and right hemispheres. With recordings from 5 electrodes positioned at equal spaces of 3 cm in a horizontal row across the scalp, VEP asymmetry in 78 albino probands and 34 non-albino controls was assessed by two methods. The first method which was qualitative consisted of visual inspection of the potential distribution across the scalp within an early time period of the response. As an adjunct to visual inspection, the reverse in sign of a difference potential from a left minus right hemispheric response following both left eye and right eye stimulation was also used. The second method which was quantitative included analysis that was based on estimation of the peak of the potential distribution across the electrode array at every time instant of the response. For this latter method the midline derivation was excluded. Several experimental parameters (e.g. mode of stimulus presentation, pattern size, field size) were investigated to determine the optimum stimulus and recording parameters for detecting albino misrouting. Under optimum test conditions, evidence of misrouting by visual inspection was found in all of the 78 albino probands tested. The quantitative analysis which provides an indication of both the presence and the degree of VEP asymmetry was used to establish population norms for various test conditions. Results of the quantitative analysis provided evidence that the degree of asymmetry in a sample of non-albino controls (including heterozygote family members) was not significant. The degree of asymmetry for albinos, however, was highly significant and was primarily restricted to a narrow time window of the response between about 80 and 110 msec following the appearance of a checkerboard pattern with elements subtending 55′ of arc. The early time course of the asymmetry and the effects of pattern size and defocus suggest that albino misrouting is reflected in the CI component of the pattern appearance response. As the CI component is thought to be generated by dipoles lying within cortical area 17, we can assume that the reflected misrouting is of a similar origin. The 100% detection rate of VEP asymmetry in albinos and 0 false positives in normal controls, heterozygote family members and non-albino patients with comparable albino symptoms (e.g. nystagmus, reduced acuity, retinal hypopigmentation), indicates that VEP asymmetry is a decisive clinical measure for the diagnosis of albinism and for differential diagnosis. The protocol for electrophysiological diagnosis and the results of its application in several atypical patients is also presented.