Electronmicroscopical examination on skin lesions of epidermolysis bullosa dystrophica recessiva (E.b.d.r.) and epidermolysis bullosa acquisita (E.b.a.) associated with Crohn's disease have demonstrated that blistering occurs between epidermis and dermis beneath the basal lamina. The structural defect concerns the anchoring fibrils only which are missing in the junctional zone of the involved skin. All other junctional structures are intact. Beneath the basal lamina a band-like zone of a moderate electrondense, amorphous material is seen in the skin-lesions of epidermolysis bullosa acquisita, less marked in epidermolysis bullosa dystrophica. Direct immunofluorescent investigation of involved skin of E.b.a. shows a pemphigoid-like fluorescent pattern at the basal lamina with antihuman IgG-, -IgM-, beta1c/beta1a and antihuman C1q-component. In epidermolysis bullosa dystrophica, however, a fluorescent pattern at the basal lamina was found only with anti-human IgG and Anti-C3. The pathogenetic importance of the immunoglobuline-deposits at the basal lamina is discussed in regard of the loss of anchoring fibrils and the subsequent vesication in these types of epidermolytic diseases.