In three patients with long-standing multiple sclerosis, bullous pemphigoid developed. The diagnosis of bullous pemphigoid was based on histologic findings, direct and indirect immunofluorescence, and Western blots showing IgG reacting with the 220 to 240 kD bullous pemphigoid antigen in the serum of three patients. Contrary to previous observations, bullous pemphigoid associated with multiple sclerosis was not different from bullous pemphigoid alone. Three similar cases have been reported previously, so the occurrence of bullous pemphigoid in patients with multiple sclerosis may be more than a coincidence.