Eight out of 12 serum samples from patients with bullous pemphigoid having basement membrane zone antibodies gave positive binding not only to the basement membrane zone but also to the basal cell membrane and/or cytoplasm as observed by complement immunofluorescence. Reaction of fluorescein labeled pemphigus vulgaris gamma-globulins, binding mainly to the lower intercellular spaces of the epidermis, was greatly reduced by the prior incubation of high-titered bullous pemphigoid sera having the reactivity to the basal cells, while that of fluorescein labeled pemphigus foliaceus gamma-globulins binding mainly to the upper and middle intercellular spaces, was not influenced by the prior application of these bullous pemphigoid sera. These results indicate that bullous pemphigoid antibodies are heterogenous and can be classified into 2 types and that some cross reaction is present between pemphigus antibodies and bullous pemphigoid antibodies having the reactivity to the basal cells.