Is it possible to measure the risk that a patient develops thrombosis in a valid and reliable way? Is the "Messskala zur Festlegung der Thrombosegefährdung" by Peter Kümpel an appropriate instrument to assess such a risk? These questions were traced with a convenience sample of 281 patients in the departments of Neurosurgery, Neurology and Obstetrics of the University Hospital Freiburg in Germany. The "Messskala zur Festlegung der Thrombosegefährdung" by Peter Kümpel was tested for validity, reliability and practicability in a nonexperimental, explorative study. The results show a high consensus in the interrater-agreement, a rather accidental agreement with the clinical view of the medical doctor and the clinical view of the registered nurse and an only statistical measurable sensitivity and specificity of the scale. The instrument "directs" the nurses' view to a number of risk factors. It supports the pupils and the beginners in nursing in a complete assessment and gives the expert nurse a possibility to control her assessment of a patient. An organisation has to decide whether and why such an instrument should be used.