Kinetics of rod pigment regeneration were studied in vivo in Fauve de Bourgogne and Albino rabbits by adapto-electroretinography (AERG). Electroretinography in the rabbit using polychromatic flashes affords the means to dissociate the response of the cones (a-wave, b1-wave: photopic function), from that of the rods (b2-wave scotopic function). After photobeachting, electroretinograms were recorded at two minutes' intervals during dark adaptation of one hour duration. Variations of b2/b1 with time of dark adaptation provide an adapto-electroretinogram giving relative measurements of rod pigment concentration at various stages of regeneration. In the present study, photobleaching was provoked by monochromatic light (at 405, 436 and 546 nm) actinometrically controlled. Studies were conducted in two Fauve de Bourgogne and two Albino rabbits. The effect of four doses, varying from 4.10(17) photon.cm-2 to 1.10(19) photon.cm-2, was measured at each wavelength on the AERG in the four rabbits. First order kinetics for rod pigment regeneration were observed, mainly at 546 nm and at high dose levels: overall regeneration rate is apparently controlled by the isomerization step. For Fauve de Bourgogne and Albino rabbits, the regeneration rate depends on the bleaching wavelength and on the dose. At high dose levels and for long wavelengths, delayed recoveries are observed in the Fauve de Bourgogne animals. However, durations of delays are shorter with monochromatic light experiments than with polychromatic light bleaching, at the same dose. Differences of ocular media transmission may be responsible for a faster regeneration process at shorter than at longer wavelengths.