Paraneoplastic pemphigus (PNP) is a life-threatening autoimmune blistering skin disease. Clinically, it is characterized by severe mucosal erosions and various cutaneous lesions associated with lymphoproliferative neoplasmas. Suprabasal acantholysis and clefts with scattered necrotic keratinocytes are the unique histopathological features. PNP patient sera recognize multiple antigens, which have been identified as the plakin protein family that includes desmoplakin, bullous pemphigoid antigen I (BPAG1), envoplakin and periplakin, and desmogleins 1 and 3. Castleman's tumor, non-Hodgkin's lymphoma, thymoma, follicular dendritic cell sarcoma and chronic lymphocytic leukemia are the commonly associated neoplasmas in PNP. We have also demonstrated that the autoantibodies reacting to epidermal proteins are directly produced by the cells in the associated tumors. Bronchiolitis obliterans is frequently found in PNP and may cause respiratory failure and death. In our experience, the early detection and removal of the tumor and i.v. administration of immunoglobulin are critical for the treatment of PNP.