Electroretinographic studies have been helpful in differentiating human forms of retinitis pigmentosa inherited by different patterns. The prognosis appears to be correlated with the mode of inheritance. The recessively inherited form along with the x-linked and dominantly inherited with reduced penetrance type of inheritance are associated with more severe forms of the disease than is the dominantly inherited with complete penetrance. The underlying biochemical defects have not been identified. Human pathological specimens early in the disease have been almost nonexistent. Animal models have been identified but correlation with human disease has been markedly limited [1]. Electrophysiology and recent technology offer some prospect for differentiating responsible abnormalities and offer a noninvasive evaluation of the disease process and treatment. Three cases of dominantly inherited retinitis pigmentosa with complete penetrance are presented. These show a decreasing B-wave amplitude on successive photopic evaluations using fast random stimuli.