Bullous pemphigoid (BP) is an autoimmune blistering disease of the skin. Several variants of BP have been described but until recently the relationship of these variants to generalized BP was unclear. Several studies have shown that pemphigoid nodularis, pemphigoid vegetans, localized BP and vesicular pemphigoid are true variants of BP as the circulating antibodies in these patients recognize the same 230 kDa BP antigen as found in patients with generalized BP. Erythrodermic BP is a very unusual variant characterized by an erythroderma along with blister formation. We describe the third known patient to develop erythrodermic BP and characterize the antigenic specificity of the circulating antibodies in both our newly reported patient with erythrodermic BP and in one of the two other previously reported cases of erythrodermic BP. Both patients with erythrodermic BP had circulating IgG antibodies which bound to the epidermal side of salt-split human skin in a pattern identical to two patients with immunopathologically proven generalized BP. Sera from four erythrodermic patients without blisters and from a healthy normal volunteer, as controls, failed to demonstrate detectable circulating IgF autoantibodies. Immunoprecipitation studies revealed that both patients with erythrodermic BP had circulating IgG autoantibodies which recognized, to varying degrees, the same 230 and 180 kDa BP antigens as recognized by sera from two patients with immunopathologically proven generalized BP. Sera from four erythrodermic patients without blisters and from a healthy normal volunteer, as controls, failed to recognize any specific polypeptides. These observations demonstrate that erythrodermic BP is a distinct clinical variant of BP.