Sera from 47 patients with PSS were studied for the presence of antinuclear antibodies. Antinuclear antibodies were present in 60 per cent of the sera in a titer of 1:16 or greater. In most cases the titer was low, but a titer of 1:256 or greater was present in sera from 6 patients. The pattern of nuclear fluorescence was most commonly that of fine or large speckles. Most sera contained both IgG and IgM antinuclear antibodies. There was no relation between duration of disease or severity of disease and the presence of antinuclear antibodies. Similarly, no correlation could be demonstrated between clinical findings and the immunoglobulin class, titer, or staining pattern of antinuclear antibody. The prevalence of high titers of antinuclear antibodies was greater in patients with hypergammaglobulinemia than in those with normal levels of gamma globulin. Rheumatoid factor was present in 33 per cent of sera. Patients with high titers of rheumatoid factor tended to have high titers of antinuclear antibodies. Antinuclear antibodies were found in low titer in 7 per cent of blood relatives less than 60 years of age. The number of sera with antinuclear antibodies was slightly higher in the nonaged relatives of patients with systemic lupus erythematosus (11 per cent), while the prevalence in relatives of patients with chronic discoid lupus (2 per cent) was similar to that of a group of healthy student nurses. The results reveal that antinuclear antibodies of a speckled pattern are commonly present in sera from patients with PSS and a p pear to be unrelated to the duration or severity of the disease. The peripheral pattern of nuclear fluorescence produced by sera from acutely ill patients with systemic lupus erythematosus was not observed with any of the sera of patients with PSS. These observations emphasize the fact that the presence of antinuclear
