Studies of cellular immunity in juvenile chronic arthritis (juvenile rheumatoid arthritis, JRA) have been scant, controversial, or have not addressed the issue of the different forms of the disease. We studied 23 patients with JRA of either systemic (n = 8) or polyarticular (n = 15) type of onset and compared the findings to those made in 10 healthy children of similar age. Both groups of patients with JRA were found to have increased CD8 T cells, normal production of interleukin-1 and 2 and decreased production of B cell stimulatory factor in their peripheral blood. In addition, patients with systemic JRA were found to have decreased spontaneously expanded and concanavalin-A induced suppressor functions. These findings in both forms of JRA are distinguishable from those that have been made in other connective tissue diseases including the adult form of rheumatoid arthritis.