Paraneoplastic pemphigus (PNP) is an autoimmune mucocutaneous blistering disease characterized by IgG autoantibodies that bind to various epithelia and immunoprecipitate a complex of 250, 230, 210, 190 and 170 kDa proteins. A recent study has suggested that PNP patients have antidesmoglein (Dsg) 3 autoantibody and that the antibody plays a pathogenic role in PNP. We report a 72-year-old woman with PNP associated with thymoma and adenocarcinoma of the lung. Diagnosis of PNP was made by the characteristic clinical, histological and immunopathological findings, as well as immunoprecipitation of characteristic 230, 210 and 190 kDa proteins. Using enzyme-linked immunosorbent assay with baculovirus-expressed recombinant proteins, the patient's serum was negative against both Dsg 3 and Dsg 1. This finding is unusual, and it suggests that the target antigen, which is involved in acantholysis, may be other than Dsg 3 in this case.