The incorporation pattern of the rabbit albumin labelled with Lissamine Rhodamine B200 or 125I into the rabbit dentine and the enamel matrices was studied by fluorescence microscopy and/or autoradiography. The fluorescence of the fluorochrome-labelled albumin was observed in the dentine at 6 hours and 3 days. Autoradiographic silver grains were observed over the predentine at 1 hour after the injection. They were found over the dentine matrix adjacent to the predentine-dentine junction at 6 hours. The silver grain band was concentrated over the internal dentine matrix at 3 days. However, an appreciable amount of the fluorescence could not be seen in the enamel at any time after the injection. Also, no significant differences in the number of autoradiographic silver grains were found over the enamel matrix between the experimental groups and the background at any time after the injection. These results suggested that albumin was incorporated into the developing dentine matrix but not into the developing enamel matrix.