We studied the frequency of antibodies to extractable cellular antigens in 90 Spanish SLE patients. Antibodies to Sm, nRNP, Ro and La were found, respectively, in 6 (6.6%), 18 (20%), 30 (33.3%) and 6 (6.6%) patients. In spite of HLA differences, these results are similar to those found by other authors in Caucasian SLE patients. Our only relevant association was the finding of severe renal disease and high frequency of anti-DNA and hypocomplementemia in patients with antibodies to Ro. Based on these and earlier findings, we discuss the possibility that the immune response to Ro in Spanish patients might be located in a unique extended HLA-complement haplotype.