Abstract: Using Western immunoblot technique, 20 BP sera were reacted with epidermal extract of normal human skin. The results showed that 18 out of 20 sera (90%) combined with a 230 KD MW protein, 5 out of 20 sera (25%) combined with a 160 KD MW protein, including 3 sera also combined with the 230 KD MW protein. Theauthors hold that the 160KDMW protein is not the break down product of the 230KD MW protein. Thi s result further indicates that BP antigens are of heterogeneity. The major BP antigen is a 230 KD MW protein. Antibodies to this antigen arc present in the majority of patients with BP. The minor BP antigen is a 160 KD MW protein. About 25% of BP patients have antibody against this antigen.