We have found that anti-SS-B/La antibodies are present in a group of patients with a characteristic recurrent annular erythema, and immunological abnormalities. The presence of a disease-specific epitope for this entity has been examined by comparing immunological reactivity of anti-SS-B/La antibodies between these patients and patients with classical Sjögren's syndrome who have anti-SS-B/La antibodies but do not have this characteristic erythema. In immunoblotting using three different antigen sources, all the sera from both groups exhibited the same reaction patterns. V8 protease mapping showed that the sera could be divided into three groups by the difference in reactivity to two main digested peptide fragments. However, no significant relationship of the reactivity in peptide mapping between the two patient groups was observed. Further studies are necessary to elucidate the role of anti-SS-B/La antibodies in disease pathogenesis in these patients, in particular by more precise peptide mapping using recombinant SS-B/La antigen proteins.