OBJECTIVE To study the dynamic changes in plasma levels of urokinase type plasminogen activator (uPA) and urokinase type plasminogen activator receptor (uPAR) and their influence on prognosis in patients with systemic inflammatory response syndrome (SIRS). METHODS In this study, a prospective clinical case control study was adopted. Eighty-five patients were divided into two groups according to diagnostic criteria of SIRS: SIRS patients (n=50) and non-SIRS patients (n=35). SIRS patients were again divided into SIRS group (n=26) and SIRS complicated by multiple organ dysfunction syndrome (MODS) group (n=24) by their severity, and survival group (n=35) and non-survival group (n=15) by their outcome . The control group comprised of 30 healthy blood donors. Venous blood samples of about 2 ml were collected at the time when non-SIRS patients were admitted, and blood samples were collected in SIRS patients on 1,3, 5 and 7 days when SIRS was diagnosed, and in the healthy control group blood samples were collected when they visited the General Health Check-up Division at our hospital. Plasma levels of uPA and uPAR were measured by enzyme-linked immunosorbent assay (ELISA), and relationship between plasma level of uPAR and acute physiology and chronic health evaluation II(APACHEII) score was analyzed using Pearson correlation. RESULTS The plasma levels of uPA and uPAR in patients of SIRS and MODS were obviously higher compared with non-SIRS and healthy controls [uPA (μg/L): 1.208±0.264, 1.120±0.276 vs. 0.744±0.190, 0.782±0.257; uPAR (μg/L): 3.704±1.018, 4.970±1.284 vs. 1.892±0.476, 1.823± 0.797, all P<0.01]. The plasma level of uPAR in MODS group was obviously higher than that of SIRS group (P<0.01). The plasma level of uPA (μg/L) in non-survival group was markedly elevated on 5 days and 7 days compared to survival group (5 days: 1.177±0.185 vs. 0.856±0.223, 7 days: 1.377±0.185 vs. 0.836±0.223, both P<0.01). The plasma level of uPAR (μg/L) in patients of non-survival group was obviously higher compared with survival group on 1, 3, 5 and 7 days (1 day: 5.301±1.410 vs. 3.888±1.015, 3 days: 4.017±0.898 vs. 2.994±0.638, 5 days: 5.032±1.238 vs. 2.536±1.017, 7 days: 5.232±1.238 vs. 3.536±1.017, all P<0.01). Correlation analysis showed that there was positive correlation between uPAR level and APACHEII score (r=0.640, P<0.01). CONCLUSIONS Coagulopathy is present in SIRS patients, the plasma levels of uPA and uPAR are high in patients with SIRS, and the increase of uPAR in patients with SIRS indicates a poor prognosis.