We have defined a HLA locus (SB) which maps centromeric to the other known genes of the HLA complex. We have continued studies on the importance of the genetic region marked by this gene in three different human diseases: dermatitis herpetiformis, systemic lupis erythematosis, and kidney transplantation rejection. Previous studies of patients with dermatitis herpetiformis have been extended particularly with respect to family analysis of complexity related to the differentiation of DR3,3 from DR3,w6 phenotypes and statistical analysis of haplotype associations. The data are most consistent with the interpretation that the HLA-linked gene tends to occur on haplotypes with DR3 and SB1, and confers risk in an autosomal recessive manner. Studies of 4 pairs of HLA-A thru HLA-DR identical sibling kidney donor/recipient pairs in whom there had been rapid rejection failed to identify SB/DR rcombinations, which would have suggested importance of SB region genes in kidney graft rejection. Pilot studies of 15 patients with SLE failed to show strong association of the disease with SB phenotype.