The clinical features and HLA types of 67 unrelated patients with Systemic Lupus Erythematosus (SLE) were analyzed. The results showed: 1. An increase in frequencies of A1, B8, and DR3. These antigens are in close linkage disequilibrium and our data show that susceptibility to SLE is associated with the presence of all three antigens, implicating the specific haplotype which bears these antigens. 2. An increase in frequency of DR2, but not A3 or B7, these latter two antigens being in linkage disequilibrium with DR2. 3. 73.3% of the 54 Caucasoid SLE group were either B8 and/or DR2. This is in comparison with 37.5% in the controls and the difference is significant (p less than 0.001). 4. There was no association apparent between extent of disease, particular organ involvement and level of circulating antibodies to double stranded DNA with any HLA region product.