The purpose of this study was to define the ultrastructural defects and pathogenesis of epidermolysis bullosa dystrophica-recessive (EBD-R). The only consistent ultrastructural alteration found in EBD-R was an absence of anchoring fibrils. In many specimens of nonblistered, nontraumatized EBD-R skin, absence of anchoring fibrils was the only ultrastructural abnormality observed. The possibility that lack of anchoring fibrils was a secondary change resulting from previous blistering and scarring was eliminated by our observation that anchoring fibrils were consistently absent in the never previously blistered skin of two newborns with EBD-R. In experimentally traumatized skin, the epidermis and dermis separated in the region of the epidermal-dermal junction normally occupied by anchoring fibrils. Basal lamina and dermal microfibril bundles appeared to be normal. Using recombinant grafts, we demonstrated that anchoring fibrils were not formed by EBD-R dermis when combined with EBD-R epidermis or normal epidermis. Anchoring fibrils were formed when normal dermis was combined with normal and EBD-R epidermis. These studies indicate that the defect in EBD-R resides in the dermis and that the defect may be associated with impaired formation of anchoring fibrils.