Objective To detect the changes of interleukin-18 (IL-18) in plasma of trauma patients and evaluate their value in early warning of organ dysfunction. Methods A prospective study was carried out in 54 trauma patients admitted in from March 2001 to September 2002, which were divided into low injury severity score(ISS) group (Group L-ISS) and high ISS group (Group H-ISS). ELISA was applied to measure the level of IL-18 of blood samples that were collected on arrival, at days 4, 7 and 14 following admission. In the meantime, IL-18 level of plasma samples from patients with systemic inflammatory response syndrome (SIRS), sepsis and multiorgan dysfunction syndrome (MODS) was retrospectively analyzed so as to calculate the critical value of IL-18 in predicting organ dysfunction. Results After trauma, IL-18 concentration of plasma reached peak at days 4 and 7, and decreased gradually at day 14, which was significantly related to SIRS, sepsis and MODS, respectively. The IL-18 level was high relatively in plasma from patients with organ dysfunction. The higher IL-18 level in plasma within seven days after trauma indicated the severer organ dysfunction. Conclusion IL-18 is sensitive in early warning of organ dysfunction after trauma.