Calbindin-27 kDa immunocytochemical localization was studied concurrently in the pineal organ and retina from human as well as representatives of all vertebrate classes. Calbindin immunoreactivity was demonstrated in retinal cones (but not in rods) and in pineal transducers (cone-like and modified photoreceptor cells, pinealocytes) of a majority of amniotes. In contrast, no labelling was observed in anamniotes, except in retinal cones of the toad. Labelling was distributed through all cellular compartments (outer and inner segments, perikarya, pedicles or processes) of pineal transducers and retinal cones. Intra- and interspecific variations of calbindin contents are discussed.