The biphasic waveform (BPW) is an abnormality of the optical transmission waveform obtained during measurement of the activated partial thromboplastin time on a specific photometric haemostasis autoanalyzer. This abnormality is related to calcium-dependent formation of complexes between C reactive protein and very low density lipoprotein. Biphasic waveform had a high sensitivity and negative predictive value for the identification of patients with severe sepsis and septic shock. On day 3, the time course of the biphasic waveform is a marker for the prognosis of sepsis-related mortality. The BPW is not a surrogate marker for C-reactive protein or procalcitonin and provides additional information. Further trials should be necessary using BPW for diagnostic and management procedures. Compared with other laboratory markers such as C reactive protein or procalcitonin, activated partial thromboplastin time waveform analysis is a tool that is rapid, inexpensive, effective and available 24 hours a day. When the analyzer is locally available, waveform analysis of this routine coagulation test provides information for the diagnosis of severe sepsis and the prognosis of septic patients.