Among the many antinuclear antibodies found among patients with systemic lupus erythematosus, a subset predominates in terms of frequency of occurrence and titer. These antibodies include anti-DNA, antihistone, anti-U1 RNP, anti-Sm and anti-Ro and they tend to occur in linked sets which correspond to their autoantigenic epitopes on the nucleosome, the U1 snRNP, and the Ro particle. This pattern of occurrence suggests that these nucleoprotein structures elicit at least some of the autoimmune responses in this disease.