A vesiculobullous eruption with clinical and histological features of bullous pemphigoid developed in a 28-year-old woman with proven systemic lupus erythematosus (SLE). Serum of this patient contained elevated titers of antinuclear antibodies but basement membrane antibodies could not be detected at first, though they did appear in blister fluid. Normal monkey skin explants cultured on this patient's sera gave positive direct immunofluorescence (IF) at the basement membrane zone (BMZ) for IgG deposits. The use of tissue culture methods may be helpful because of the capacity of this test system to reveal the presence of the antibodies to the BMZ despite the presence of the antinuclear antibodies that appear to interfere with their demonstration in standard indirect IF tests.