The electroretinogram (ERG) is the only test currently available that has the potential to identify patients with Usher syndrome before onset of fundoscopic and visual abnormalities. The ERG is a noninvasive technique that can diagnose retinitis pigmentosa via measurement of corneal-retinal potentials. Forty-seven children with bilateral severe to profound sensorineural hearing loss were evaluated. Usher syndrome was diagnosed in five children, all of whom subsequently underwent cochlear implantation. We have found that accurate diagnosis of Usher syndrome in infants and young children is possible via ERG. Benefits of early diagnosis include timely counseling regarding genetic issues, educational and vocational placement, and cochlear implantation. For this reason we recommend that all newly identified children with bilateral severe to profound sensorineural hearing loss undergo ERG testing.