Thirty-six patients with bullous pemphigoid (BP) have been periodically evaluated for four years. This study demonstrates that BP may occur in a transient predominantly localized form that remits spontaneously, and most BP patients after successful therapy remain in prolonged clinical remission. In this study, all patients with active or recurrent disease had IgG and/or C3 basement membrane zone (BMZ) deposition. Serum anti-BMZ antibodies was an inconstant feature. In most instances, clinical remission of BP was associated with disappearance of BMZ ig and C3 deposition and serum BMZ antibodies. Fluorescein-conjugated, antihuman C3 appears to be a more sensitive immunoreagent than antihuman, class specific, immunoglobulin antisera in detecting positive BMZ staining in BP. Combined therapy with azathioprine plus prednisone appears to be superior to prednisone alone in the treatment of BP.