Introduction: Inflammation and coagulation are closely linked, and both can be triggered by endotoxin. Thrombelastometry and impedance aggregometry are of diagnostic and predictive value in critically ill patients. In this observational study we investigated the correlation of endotoxin activity with thrombelasometric and aggregometric variables in patients with systemic inflammation.Methods: Based on a daily screening on a tertiary academic surgical ICU, patients, as soon as they fulfilled two or more criteria for systemic inflammatory response syndrome (SIRS), were included. In whole blood we performed endotoxin activity (EA) assay, thrombelastometry (ROTEM®) and impendance aggregometry (Multiplate®).Results: In total, 49 patients were included with a broad spread of EA levels of (median (minimum to maximum)) 0.27 (0.01 to 0.72), allowing expedient correlative analysis. Clot formation time (CFT) (263 s (60 to 1,438 s)) and clotting time (CT) (1,008 s (53 to 1,481 s)) showed a significant negative correlation with EA level (r = -0.38 (P < 0.005) and r = -0.29 (P < 0.05)). Positive correlations were found for alpha-angle (50° (17 to 78°), r = 0.40 (P < 0.005)) and maximum clot firmness (MCF) (55 mm (5/76), r = 0.27 (P < 0.05)). No significant correlations were found between Lysis Index at 60 minutes (LI60) and EA levels. There was no correlation between EA level and aggregometric values, or classical coagulation parameters.Conclusions: In patients with systemic inflammation, increasing endotoxin concentrations correlate with increased clot formation.