The blisters of 2 cases of bullous pemphigoid were examined electron microscopically. Specimens were taken from fresh blisters, grossly normal skin surrounding the blister, and from a mechanically moved blister (Asboe-Hansen phenomenon). The blisters occupied the space between the cell membrane of the basal epidermal cells and the dermal membrane. No discontinuities in these structures were found. The filaments anchoring half-desmosomes to the dermal membrane (anchoring filaments) were torn in the fresh blisters. The same filaments were torn in the blisters spread by finger pressure. Change in the elastic fibril system may be the fundamental lesion in bullous pemphigoid.