Haemostatic changes in septic patients are complex, with both procoagulant and anticoagulant changes. Thirty-eight patients with severe sepsis and 32 controls were investigated by coagulation screens, individual factor assays, calibrated automated thrombography (CAT), whole blood low-dose-tissue factor activated (LD-TFA) Rotem and LD-TFA waveform analysis. Thirty-six of 38 patients had an abnormal coagulation screen. The mean levels of factors II, V (P < 0·05), VII, X, XI and XII, antithrombin and protein C (P < 0·01) was decreased in sepsis compared with controls. The mean factor VIII and fibrinogen level (P < 0·001) was increased. CAT in platelet rich and poor plasma showed a prolonged lag time (P < 0·02), decreased peak thrombin (P < 0·02) and delayed time to peak thrombin (P < 0·001) in sepsis patients, however, the endogenous thrombin potential was equivalent in sepsis and controls. In LD-TFA Rotem, septic patients had delayed clot times (P = 0·04) but an increased maximum velocity of clot formation (P < 0·01) and area under the clot elasticity curve (P < 0·01). LD-TFA waveform analysis showed a delayed onset time but an increased rate of clot formation (P < 0·005). In conclusion, global tests of haemostasis suggest that in this patient group, activation of haemostasis is delayed but once initiated thrombin generation and clot formation are normal or enhanced.