Serum dehydroepiandrosterone sulphate (DHEAS) levels and diagnostic autoantibody titers were measured in patients with pemphigoid/pemphigus [n = 46/4; 21 men and 29 women, 42 to 93 years of age (mean 79)]. Twenty-four patients were either on peroral Prednisolone (n = 11), or topical treatment with betamethasone (n = 13), and the other 26 were either receiving non-steroidal drugs or were untreated. Their DHEAS levels were compared to those of 20 patients with psoriasis, and to 23 patients with secondary osteoarthritis (OA). Assessing the patients by group, the mean DHEAS level was markedly lower in the pemphigoid/pemphigus than in the psoriasis and OA patients (geometric mean 600 vs. 2130 and 2100 nmol/l, respectively; p < 0.001). This difference was independent of steroid treatment. No correlation was found between the DHEAS levels and antibody titers. The low levels found in pemphigoid/pemphigus are concordant with those reported for systemic lupus erythematosus, rheumatoid arthritis and polymyalgia rheumatica/giant cell arteritis. DHEAS deficiency is a permanent feature in these autoimmune diseases, and may contribute to their etiology and/or pathophysiology.