A 35 yr old black man presented with a generalized eruption of lichen planus; subsequently tense blisters appeared within the lichenoid lesions and on clinically normal skin. Histopathological characteristics of lichen planus were present in the papules, and those of bullous pemphigoid were seen in the bullae taken from non-lichenoid skin. Direct immunofluorescence studies revealed immunological characteristics of lichen planus in skin and mucosal lesions of L.P. [lichen pemphigoides]. Bound Ig[immunoglobulin]G and .beta.1C/.beta.1A with tubular patterns were detected at the dermo-epidermal junction in all the skin fragments (clinically normal skin, bullous lesions lichenoid skin and mucous lesions). Indirect immunofluorescence studies showed at several intervals that the patient had circulating antibasement membrane zone antibodies (IgG; titers 1/50). This is the 3rd published case in which immunofluorescence studies established the pemphigoid nature of some bullous lichen planus. These findings indicate an immune disorder in lichen planus.