• Electroretinography (ERG) has been utilized to claim that the various hereditary subtypes of retinitis pigmentosa (RP) could be distinguished according to the temporal characteristics of the b wave. This study compares two different ERG techniques, one utilizing constant amplitude response and the other balanced photopic and scotopic stimuli, for the early diagnosis of RP. Both methods were found to be reliable objective tests for diagnosing RP. Neither test could differentiate between dominant, autosomal recessive, or X-linked RP.