The term thrombelastograph (TEG) was used to describe the trace produced from the measurement of the viscoelastic changes associated with fibrin polymerization. Recently the term rotational thromboelastometry has been applied to the output of the ROTEM instrument. Since its first description in 1948, the TEG/ROTEM has been successfully used in the near patient assessment of haemostasis. The greatest use has been the application of TEG-guided transfusion of blood components in hepatic and more widely in cardiac surgery. Recent years have seen a renewed interest in the technology with applications for both pharmaceutical monitoring and patient screening being described. The present review gives a broad overview of the developments and applications related to thrombelastography/thromboelastometry.