OBJECTIVE To monitor longitudinally the concentrations of cytokines in the plasma of patients with severe burns. METHODS Prospective open study. METHODS Burns unit, university hospital, Norway. METHODS 27 patients (5 women and 22 men, mean age 37 (range 13-82) years). METHODS Measurement of plasma concentrations of interleukin-1beta(IL-1beta), interleukin-1 receptor antagonist (IL-1ra), interferon-7(IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) were measured by enzyme linked immunosorbent assays (ELISA). METHODS Changes in concentrations, and correlation with morbidity and mortality. RESULTS The concentration of IL-1beta and IL-1ra were increased in all patients and highest at the time of admission. Initially there was little or no circulating IFN-gamma, but this increased from day 5-10 in all patients. Only 8/15 patients had transient increases in circulating TNF-alpha. Concentrations of IL-1ra correlated with total burn surface area (TBSA) and area of third degree burn, as well as with plasma concentrations of C - reactive protein (CRP). Concentrations of IL-1beta and IL-1ra were higher in patients who developed infective complications than in those who did not (interleukin-8 (IL-8) has previously been shown to follow this pattern as well). Patients who survived had significantly higher IL-1beta concentrations than those who died (13(1) compared with 3 (1) pg/ml, p = 0.005) CONCLUSIONS There are significant time-dependent changes in plasma concentrations of IL-1beta, IL-1ra, IFN-gamma and TNF-alpha after serious burns. IL-1ra concentrations may be influenced by size of the burn and the acute phase response; IL-1beta, IL-1ra and IL-8 may have a role in the host's response to infection; and IL-1beta may influence outcome.