The serologic and clinical features of patients from pedigrees multiplex for systemic lupus erythematosus (SLE) were evaluated among three ethnic groups: Hispanics, African-Americans and European-Americans. Data were obtained from a registry of 123 pedigrees, composed of 4 Hispanic, 40 African-American and 79 European-American pedigrees. All patients met at least four criteria for the diagnosis of SLE per the American College of Rheumatology. Clinical information was obtained through review of the medical records and questionnaires completed by the participants. Ethnicity by self-identification was found to be an important factor influencing the prevalence of serologic results and clinical features. Anti-nRNP occurred more frequently in African-Americans (45.7%) than in European-Americans (7.5%) or Hispanics (0%) (p<0.0000001), as did anti-Sm (18.5% vs 1.6% and 0%, respectively) (p<0.000001). Malar rash, photosensitivity and oral ulcers were most frequent in the Hispanic population while proteinuria and leukopenia predominated in the African-American population. Arthritis and lymphopenia were present in a similar proportion in all ethnic groups. These results show that many of the ethnic differences known for isolated cases of SLE are also present in familial cases of SLE.