Seven patients with Oguchi's disease were examined by conventional full-field rod and cone electroretinograms (ERGs), spectral characteristic studies with photopically matched short- and long-wavelength stimuli (3 of the 7 patients) and electrooculogram (EOG) (6 patients). ON and OFF photopic ERG responses, recorded with rectangular stimuli, in 3 patients were compared with those of 13 normal subjects and 13 patients with complete congenital stationary night blindness (CSNB). Conventional full-field ERGs recorded after 30 minutes of dark adaptation revealed absent rod, but essentially normal cone and flicker ERGs in all patients. With the dark-adapted standard flash ERG, the a-wave amplitude was significantly lower than normal in all patients. The spectral characteristic study indicated that the ERG recorded after 30 minutes of dark adaptation represented cone activity. The EOG was abnormal in all patients examined. The ON and OFF responses of the photopic ERG were normal in Oguchi's disease patients; however the ON responses were reduced in patients with complete CSNB. The absence of a rod a-wave, with the abnormal EOG, strongly suggests that the rod itself is abnormal in Oguchi's disease. This finding differs from the report by Carr and Gouras (1965) and Carr and Ripps (1967). The normal ON and OFF responses in the photopic ERGs of Oguchi's disease patients contrast with those of the complete CSNB patients in whom only the ON response is reduced.