Tissue injury results in the release of the intracellular protein actin which is cleared from the circulation by the plasma proteins gelsolin and Gc-globulin, constituting the Extracellular Actin Scavenger System (EASS). Experimental studies have shown that excessive amounts of actin in the circulation can lead to a condition resembling multiple organ dysfunction syndrome (MODS), and we have previously demonstrated that the level of Gc-globulin is decreased after severe trauma. The purpose of the present study was to determine whether the plasma levels of gelsolin were altered in the early phase after trauma. Twenty-three consecutive trauma patients were studied. Plasma samples were assayed for gelsolin by immunonephelometry with polyclonal rabbit antihuman gelsolin prepared in our own laboratory. The median time from injury until the time the first blood sample was taken was 52 min (range 20-110) and the median Injury Severity Score (ISS) was 20 (range 4-50). The gelsolin level on admission was reduced significantly in the trauma patients compared with normal controls. The median level was 51 mg/L (7-967) vs. 207 mg/L (151-621), P <0.0001. There was no correlation between admission levels of gelsolin and ISS or survival. This study illustrates that the plasma concentration of gelsolin is significantly diminished immediately after traumatic injury. Further studies are necessary to establish a role for gelsolin or EASS in the development of MODS in trauma patients. The level of serum or plasma gelsolin can be determined rapidly and accurately using a nephelometric assay.