Anti-p200 pemphigoid is a rare subepidermal blistering disease associated with autoantibodies against a 200-kDa protein, reportedly corresponding to laminin γ1. However, direct evidence of the pathogenic potential of these antibodies has not been proven. For 5 years we have followed up a patient with anti-p200 pemphigoid. During this period she experienced a total of three generalized relapses. Quantifying our patient's autoantibody concentrations against laminin γ1 by enzyme-linked immunosorbent assay throughout the course of her disease we demonstrated a clear correlation with disease activity, thus providing the first evidence of the possible pathogenic role of antibodies against laminin γ1 in anti-p200 pemphigoid. Further analysis by Western blotting revealed the occurrence of additional autoantibodies against the α3 chain of laminin 332, 1·5 years after diagnosis, suggestive of intermolecular epitope spreading. Yet, the clinical appearance was unchanged and mucous membranes remained unaffected at any stage of the disease.