In the present study, we investigated the kinetics and the activation thresholds for the production of a number of pro-inflammatory cytokines and cytokine antagonists in Escherichia coli lipopolysaccharide (LPS) or phytohaemagglutinin (PHA) stimulated whole blood cultures of 13 patients with systemic juvenile chronic arthritis (SJCA) and 10 healthy children. In unstimulated cultures, the levels of interleukin (IL)-1beta, IL-6 and tumour necrosis factor alpha (TNF-alpha) were undetectable in both groups, suggesting that there was no spontaneous production of these cytokines by circulating leucocytes. The activation thresholds for the production of these cytokines, as well as the capacity for production, did not differ significantly between patients and controls. The level of interleukin-1 receptor antagonist (IL-1ra) in plasma of the patients was significantly elevated, while the in vitro production of IL-1ra was essentially normal and it did not correlate with plasma levels of IL-1ra. Supernatant levels of soluble TNF-alpha receptor (sTNF-R) I and II were both significantly elevated and correlated with the global activity score. In contrast, the supernatant levels of IL-10 were reduced in both PHA- and LPS-driven cultures. Although IL-10 levels did not correlate with laboratory or clinical indices of disease activity, the results suggest that reduced IL-10 production may play a pathogenetic role in SJCA.