In neurosurgery, none of the drugs used in other specialties as prophylaxis of thrombo-embolism have found general acceptance. Certain centers reject any drug prophylaxis of thrombo-embolism. Others treat many or--with the exception of subarachnoid hemorrhage--almost all patients according to the Kakkarscheme. Many aim for an individual examination of the risk of early mobilization and, if necessary, combine mechanical and medicinal methods (Tab. 3). No center has published any systematic studies of substantial patient populations. It is not possible to draw any medico-legal conclusions from the neurosurgical literature available. The multitude of diagnostic and therapeutic regimes, sometimes accompanied by contradictory publications, means that even non-neurosurgeons regard neither the diagnosis nor the treatment of thrombo-embolisms as ideal. Even under low-dose heparinization, deep venous thromboses can occur, and it is in principle difficult to refute the contention that this fact changes nothing whatsoever for high-risk patients as far as the incidence of pulmonary embolism ot the occurrence of significant thrombo-embolic events is concerned. Cost calculations have proved that general thrombo-embolism prophylaxis is more expensive than individual thrombosis treatment as necessary (although there are statements to the contrary). It can, however, be stated that additional costs with the aim of improving or maintaining the quality of life would be economically justifiable if a preventive effect were proved. For modern neurosurgery, however, this neither holds true generally nor for a specific subgroup. The state of research would seem to suggest that a prospective, controlled study of neurosurgical patients, primarily in a relatively low-risk group, is necessary, advisable, and justifiable.