We have characterized a clinical significance of anti-U3RNP, anti-7-2RNP, anti-RNA polymerase I and anti-PM-Scl antibody, autoantibodies to nucleolar proteins detected by immunoprecipitation method in patients with systemic sclerosis (SSc). In 248 patients with SSc, anti-U3RNP antibody was positive in 9 (3.6%), anti-7-2RNP antibody was positive in 7 (2.8%) and anti-RNA polymerase I antibody was positive in 3 (1.2%). But none of 248 patients was positive for anti-PM-Scl antibody. Anti-U3RNP antibody positive SSc patients showed significantly lower frequency of joint and lung involvements, compared with anti-U3RNP antibody negative SSc patients. Anti-7-2RNP antibody was found only in patients with limited scleroderma. The anti-7-2RNP antibody could be detected before appearance of skin thickening, so this indicate the usefulness of detecting anti-7-2RNP antibody in the early stage of SSc. Two of 3 anti-RNA polymerase I antibody positive patients were classified as diffuse scleroderma. All anti-RNA polymerase I antibody positive patients had high incidence of internal organ involvements including lung, heart and kidney, so two of these patients died of heart failure. These data showed the close clinical association of antigenic specificities of anti-nucleolar antibodies analysed by immunoprecipitation method, and indicated the usefulness of detecting these anti-nucleolar antibodies in subgrouping of patients with SSc.