Recent major advances in understanding the genetic structure of the human leukocyte antigen (HLA) region and how HLA molecules contribute to immune responses have been paralleled by more precise identification of specific HLA genes conferring susceptibility to the various forms of juvenile rheumatoid arthritis (JRA). This article presents current models for HLA-associated autoimmune disease susceptibility and summarizes the HLA Class II alleles currently known to be associated with JRA: primarily DR8, DR5, DR6, and DPw2.1 in pauciarticular onset JRA; and DR4 in rheumatoid factor-positive polyarticular onset JRA. Rheumatoid factor-negative polyarticular onset JRA and systemic onset JRA are variously associated with several of these same genes. Gene interactions and the clinical utility of HLA typing in this disease are also discussed.