T-cell-specific adapter protein (TSAd) involved in the negative control of T-cell activation is encoded by the SH2D2A gene. Our recent studies indicate that homozygosity for short (ie GA(13) and GA(16)) alleles of the SH2D2A gene promoter is associated with development of multiple sclerosis. To study whether the same SH2D2A promoter polymorphism also contributes to the genetic susceptibility to develop juvenile rheumatoid arthritis (JRA), we examined 210 JRA patients and 558 healthy unrelated controls from Norway. The frequency of the short allele GA(13) was increased among the JRA patients compared to control (0.098 vs 0.05; P(n=8)=0.042). There was a significant increased frequency of HLA-DRB1(*)08-positive patients carrying two copies of 'short' alleles GA(13) and/or GA(16) compared to healthy controls (16% vs 6%; P(n=4)=0.016). Our data indicate that the 'short' alleles of the SH2D2A promoter could contribute to the genetic susceptibility to JRA.