The Golgi auto-antigens recognized by five human autoimmune sera were characterized with anti-Golgi auto-antibodies. The five sera showed strong anti-Golgi reactivity, together with weak anti-nuclear reactivity, as assessed by indirect immunofluorescence using the human HEp2 epithelial cell line. The Golgi auto-antigens recognized by the autoimmune sera were identified by immunoprecipitation and immunoblotting of post-nuclear supernatants. These sera reacted with at least 14 components of molecular mass (M(r)) 35-260 kDa; three components were detected only by immunoprecipitation, six components detected only by immunoblotting and five components appear to be detected by both techniques. We have previously shown that a patient with Sjögren's syndrome has auto-antibodies specific for a 230 kDa Golgi auto-antigens; a bacterial fusion protein containing auto-epitope(s) of this Golgi auto-antigen is not recognized by the other four autoimmune sera. Taken together, this study shows that the five anti-Golgi autoimmune sera recognize distinct sets of auto-antigens which include both conformational and/or sequential epitopes.