The aim of this study was to monitor the development of coagulation abnormalities in patients with severe sepsis using thromboelastometry and to assess whether increased endotoxin activity was associated with a change in coagulation. Data collected on ICU admission, day 2, 3, and 4 were analysed in 61 patients. Thromboelastometry made it possible to identify patients with a normal (group 1), hypercoagulable (group 2), or hypocoagulable (group 3) pattern. The best accuracy of thromboelastometry parameters as potential indices of coagulation abnormalities was yielded by the clot formation time and maximum clot firmness. The mortality rate was low in group 1(16%) and the presence of abnormalities, indicating either a hyper or hypocoagulation pattern, was associated with significantly higher mortality (42 and 39% respectively; P = 0.05). In group 1, baseline endotoxin activity was low [0.22 endotoxin activity units (EAU), 0.15–0.43] and did not change significantly during the observation period. In group 2, baseline endotoxin activity was elevated (0.52 EAU (0.39–0.62)) and remained high on day 2, 3, and 4. In group 3, baseline endotoxin activity was elevated (0.56 EAU (0.28–0.80)) and similarly to group 2, remained high on day 2, 3, and 4. The presence of coagulation disorders indicates a high-risk subpopulation of critically ill patients as reflected in significantly higher mortality rates and increased endotoxin activity.