A 60-year-old woman with clinical features of desquamative gingivitis had a history of painful, blistering gingival lesions for more than 2 years. There were no other accompanying mucosal or skin lesions. Clinical examination revealed erythematous and edematous gingiva with ulcerated areas and evidence of intact and ruptured bullae. White plaquelike lesions were also noted. Gingival manipulation caused epithelial desquamation. Light microscopic examination of biopsy specimens from the perilesional gingival tissue showed separation of the oral gingival epithelium and connective tissue at the margin of the collapsed bulla. A moderately intense inflammatory infiltrate was present in the connective tissue. Direct immunofluorescent microscopy revealed a continuous linear deposition of immunoglobulin G and C3 at the basement membrane zone. On the basis of clinical, histopathologic, and immunofluorescent findings, the diagnosis of mucous membrane pemphigold was made.