Ultrastructural examination was performed in 42 biopsy specimens from 22 patients with the Hallopeau-Siemens types or with the inverse type of epidermolysis bullosa dystrophica recessiva. The patient group consists of 8 cases of the localized Hallopeua-Siemens type, 9 of the generalized Hallopeau-Siemens type and 5 of the inverse type. The origins of the biopsy specimens are involved, intact and experimentally frictioned skin from blister-predilected sites, as well as clinically normal skin from nonpredilection sites. It is confirmed that all the blisters initiate below the basal lamina. Anchoring fibrils are moderately to markedly decreased in most cases, while they are normal in 3 other cases. It is thought that secondary degradation of anchoring fibrils and/or collagen fibrils plays an important role in blistering mechanism in the Hallopeau-Siemens and inverse types of recessive dystrophic epidermolysis bullosa, whereas a primary aplasia of anchoring fibrils as causative defect has been out ruled.