It is the capacity to generate thrombin, and the enzymatic work that thrombin does, that determines blood coagulability. Therefore, measurement of the enzymatic work potential of thrombin provides a method for quantifying the composite effect of the multiple factors that determine coagulation capacity. The application of measurement of thrombin generation to clinical decision making has been hampered by numerous technical difficulties and pitfalls, many of which have now been overcome. Technical advances now permit rapid, reproducible measurement. A review of clinical studies performed to date indicates the need to appreciate the precise methodology used in each case and the need to consider standardisation in future studies. Applying thrombin generation measurement to clinical decision making will require up-to-date estimates of risks relating to the disorder and the intended therapeutic intervention. Ultimately management studies will be required if the clinical utility of measurement of thrombin generation is to be proven.