BACKGROUND: Thromboelastography (TEG) measures the viscoelastic properties of clotting blood, displaying a visual trace of all phases of coagulation and fibrinolysis. When performing a TEG, it is commonly recommended to store whole blood at 37oC with only a 3-6 min delay after sampling. However, it is difficult to actually keep this recommend time and temperature. The purpose of this study is to investigate the effects on TEG by inadvertent technical errors due to inappropriate measurement time and temperature. METHODS: Twenty healthy male volunteers were studied. TEG measurements were performed at: stat, 4 min, and 8 min at room temperature, and 4 min and 8 min at 37 degrees C. Parameters used were: reaction time (R), clot formation time (K), maximal amplitude (MA), clot formation velocity (alpha-angle), clot lysis 60 min (LY60) and TEG index. RESULTS: When compared with the routine recommendation, 4 min lag time at 37 degrees C, R and K were shortened and alpha angle and LY60 were increased at 8 min after the sample. However, temperature differences did not significantly affect TEG parameters. CONCLUSIONS: Inappropriate measurement temperature does not result in significant changes of TEG parameters, but, delayed storage resulted in a false hypercoagulation state and increased fibrinolysis.