The fixation of pemphigus antibodies was revealed by indirect immunofluorescence in shedding grass snake epidermis. The antibodies of patients with pemphigus vulgaris (PV) were specifically binding to the antigenic substance which appears in the snake epidermis at the initial stage of integument change. At the peak of shedding, the fixation of PV antibodies was observed only in the upper layers of the ‘old’ epidermis although the intensity of fluorescent staining was considerably reduced. At the same stage of shedding, there was marked fixation of antibodies of patients suffering from pemphigus foliaceus (PF).The specific binding of PF antibodies was noted predominantly on the cell membranes of the ‘old’ keratinocytes, localized in the upper layers of the epidermis. In contrast to bullous pemphigoid antibodies, PV and PF antibodies failed to fix in the skin of the snake prior to or after physiologic shedding. The data obtained suggest that pemphigus may have an atavistic