In order to ascertain whether the HLA-DP locus plays a role in the genetic predisposition for systemic lupus erythematosus (SLE), 42 patients with SLE were typed for 17 different DPBeta haplotypes by locus specific amplification followed by allele specific oligonucleotide hybridization. Sera from the same patients were assayed for the presence of autoantibodies to Sm, RNP, Ro, La and of anticardiolipin antibodies (aCL). DPB1*0301 and DPB1*1401 were increased in patients compared with 107 healthy controls, mainly in those anti-Sm/RNP positive and aCL positive. Remarkably, DPB1*1401 and DPB1*0301 have a nearly identical nucleotide sequence, suggesting that an epitope shared by their membrane products is of major importance for the DP related susceptibility to SLE.