The spectral sensitivity of the ERG c-wave was studied in the chicken under yellow or red light adaptation of various intensities, ie, 1, 3, 4 and 5 W/m2 at the corneal surface in the former, and 3, 4 and 5 W/m2 in the tatter. The peak wavelength of the spectral sensitivity curve of the c-wave amplitude under both yellow and red tight adaptations was 520 or 540 nm, being shorter as compared with the peak wavelength (560 nm) under white tight adaptation (Fukuda, 1989). Under the yellow or red light adaptation the sensitivity of the c-wave was suppressed at a range of longer wavelength, suggesting a possible isolation of the blue and green cone-driven c-wave responses. The peak (520 or 540 nm) and the shoulder (580 nm) in the spectral sensitivity curves were presumed to be derived from the three cone systems.