of adult respiratory distress syndrome (ARDS) in critically ill patients. Cytokines involved in the early phase include tumor necrosis factor alpha (TNFa) and selected interleukins. Experimental infusion of TNFa has been shown to cause ARDS and increased concentration of cytokines in the lungs of the patients with ARDS has been described in both early and late phase of lung injury. The aim of this study was to evaluate the plasma levels of TNFa in patients with acute lung injury (ALI) who are at the risk of developing ARDS. We expected to observe higher and/or increasing TNFa plasma levels in patients with subsequent ARDS development. METHODS: We prospectively studied 13 critically ill patients requiring ventilatory support with sign of acute lung injury (paO 2 /FIO2 = at the time of admission to ICU. Plasma levels of TNFce were measured at 4,8,12 and 24 hours after admission to ICU (T4, T8, T12, T24). Subsequent development of ARDS (paOs/FIOZ 5 150), Apache II Score, length of ventilatory support and clinical outcome were also calculated. Results are expressed as mean ± SD. Student t-test or Mann-Whitney Rank Sum test (where appropriate) were used for statistical analysis, p< 0.05 was considered statistically significant. RESULTS: Of the 13 patients 6 patients subsequently developed ARDS (Group ARDS), 7 patients did not (Group ALI). There were no significant differences in TNF alpha plasma levels between both groups. Values of TNF a plasma levels in pg/m1 during first 24 hours after admission are presented in the table. Time T4 18 T12 T24