The V beta chain repertoire in peripheral blood T-cell was analyzed in 23 patients with juvenile rheumatoid arthritis (JRA). Of these, 15 patients had active disease as defined by tender and swollen joints. The ESR was elevated in all but three patients, C-reactive protein (CRP) was elevated in eight. Three patients were investigated during active and inactive phases of the disease. In the active phase of the disease T-cell composition was characterized by an increased number of CD4+ helper cells due to a marked increase in the CD4+CD45RA+ subgroup (34.0 +/- 10.9%, P < 0.001) and a decrease in CD8+CD29+ T-cells (10.3 +/- 5.6%, P < 0.05) compared to controls (15.4 +/- 10.0% and 17.8 +/- 12.3%, respectively). Using the monoclonal antibodies available to determine T-cell receptor (TCR) expression, patients with active disease demonstrated a significant predominance of T-cells bearing TCRs of the V beta 5 family as determined by flow cytometry (7.6 +/- 6.7 vs 3.4 +/- 1.3 in controls, P = 0.01). In active polyarthritis, up to 24% of peripheral blood T-cells expressed TCRs of the same family. In the majority of JRA patients and especially in non-active disease, no preferential TCRs were found compared to controls. However, even defining only a part of TCRs by immunofluorescence, in certain patients a preferential or dominant expression of a single V beta gene family in the T-cells was found, supporting the concept of an involvement of T-cells in the autoimmune pathogenesis of JRA.