Bullous pemphigoid is an autoimmune blistering dermatologic disease characterized clinically by tense bullae that may develop on normal or erythematous skin. The major histologic feature is a subepidermal blister with variable degrees of dermal inflammation. Other immunologically mediated blistering skin diseases may mimic bullous pemphigoid, including herpes gestationis, cicatricial pemphigoid, dermatitis herpetiformis, and epidermolysis bullosa acquisita. These diseases will be discussed. Most patients with bullous pemphigoid demonstrate circulating autoantibodies reactive with an antigen located in the lamina lucida region of the basement membrane zone. Complement activation by these autoantibodies initiates influx and activation of mast cells along with other inflammatory cells. Tissue injury with damage and eventual destruction of the basement membrane occurs as a result of the release of inflammatory mediators. The final result is subepidermal blister formation. The course of bullous pemphigoid tends to be self-limited, and successful treatment is usually effected with systemic glucocorticosteroids.