Intervention for clotting and bleeding disorders is costly, and clear-cut regimens undefined. The margin of safety between hemostasis and thrombosis is narrow and unpredictable. The use of a laboratory test to help define therapeutic regimens, dissect effects of these treatments, and to differentiate them are clearly needed. The current state of the art of thrombin generation is ready to do this. Copyright (C) 2003 S. Karger AG, Basel.