The presence and concentration of selected cytokines (interleukin 4 (IL-4), interleukin 6 (IL-6), interleukin 8 (IL-8), granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) were evaluated in the sera of 12 burned patients (6-90 per cent body surface area). The presence of cytokines in the sera of 20 healthy volunteers (control group) was always undetectable (< 2 pg/ml). In sera of the burned patients the concentrations of IL-4 or GM-CSF were also below the test sensitivity levels, while G-CSF and IL-6 were present throughout all the observation period and IL-8 was detectable at the onset of massive infections. The serum concentrations of G-CSF and IL-6 increased during the episodes of clinically and bacteriologically detectable infections. Their increases were, however, observable 12-24 h later than the other infection symptoms. Similar increases in G-CSF and IL-6 levels have been detected during corrective surgery (covering of granulation tissue with skin grafts). It may be concluded that serum G-CSF and IL-6 levels in burned patients may be considered as diagnostic factors, but the delays in the reaction to the massive infection do not allow us to use them for predicting the time of onset of the infection.