We investigated the ultrastructural distribution of sulfated glycosaminoglycans in the epithelial-mesenchymal interface of tooth germs by use of the high-iron diamine thiocarbohydrazide silver proteinate (HID-TCH-SP) staining and enzymatic digestion method. At an early stage in odontoblast differentiation, HID-TCH-SP stain deposits were sparsely distributed in the basement membrane and in the intercellular spaces. Subsequently, as formation of the initial predentin matrix began, HID-TCH-SP stain deposits were densely distributed in the interfibrillar spaces and the basement membrane. Testicular hyaluronidase digested most of those in the progenitor pre-dentin, whereas those in the region of basal lamina resisted enzymatic digestion. Testicular hyaluronidase-resistant HID-TCH-SP stain deposits were susceptible to heparitinase, indicating that the sulfated glycosaminoglycan in the basal lamina is heparan sulfate. Furthermore, the heparan sulfate tended to be regularly arranged at the sites of internal and external lamina densa. However, as progenitor pre-dentin matrix formation proceeded, the numbers of stain deposits temporarily increased and their distribution pattern became irregular, finally tending to disappear with the disruption of basal lamina.