Antibodies to nonhistone nuclear antigens are found with increased frequency in the serum of patients with systemic lupus erythematosus (SLE) and their first degree relatives. We measured the prevalence of ANA and antibodies against DNA, RNP, Sm, SSA, and SSB as well as antilymphocyte antibodies (ALA) in the serum of 24 patients with childhood onset SLE and 94 of their first degree relatives and compared the prevalence of these same antibodies in 8 patients with adult onset SLE and 33 of their first degree relatives. Antibodies against DNA, RNP, and Sm occurred more frequently in the serum of adult onset SLE patients. Among the first degree relatives ALA occurred more frequently in the sera of relatives of patients with childhood onset SLE, and parental antibodies to SSA were associated with the occurrence of childhood onset SLE in 3/24 cases. Since antibodies to SSA have been shown to be related to neonatal SLE their possible relationship to childhood SLE requires further study.