We have recently shown in a cohort of patients (n = 67) with mucous membrane pemphigoid, 63 of whom had cicatricial pemphigoid (CP), that the presence of both IgG and IgA circulating antibasement membrane zone antibodies was associated with a more severe and persistent disease. In this study we sought to ascertain whether in CP, serial titres of IgG and IgA might provide a reliable marker of disease activity. Serum titres for IgG and IgA antibodies were assayed at 6- to 12-monthly intervals in 56 patients over 32.2 +/- 20.3 (mean +/- SD) months. Antibody titres were correlated with the clinical score recorded at each follow-up visit. Sequential titres for both IgG (P < 0.001) and IgA (P = 0.015) were significantly associated with variations in disease activity. Greatest improvement was seen in patients with the greatest change in either IgG or IgA antibody titre. We suggest that serial antibody titres may therefore be useful in the assessment and management of CP.