We have studied the restriction fragment length polymorphisms (RFLP) of DR and DQ genes in HLA-DR3 positive patients with Graves' disease (GD) or Systemic Lupus Erythematosus (SLE) and compared them to those obtained in DR3 positive normal controls (N). A total of 28 GD patients, 22 SLE, and 24 N were studied. Genomic DNA was digested with BamHI or TaqI restriction enzymes and hybridized with DRB, DQB, or DQA probes. Haplotype distribution between the groups was comparable. No significant differences were found between the fragments obtained in GD and SLE compared to N. In conclusion, there were no specific DR3 polymorphisms detected by RFLP under these conditions in either of the 2 autoimmune disorders.