The immunogenetic basis of pauciarticular-onset juvenile rheumatoid arthritis is unclear. We therefore analyzed the HLA and T cell receptor genes present in a clinically well-defined group of patients. We found that the DR8 haplotype contributes most of the HLA-associated risk, although alleles at other loci contribute independently. A candidate disease-associated T cell receptor polymorphism, in contrast, was not identified in this population. Mechanistic implications of these findings are discussed.