Surgery on the superficial venous system due to uncomplicated varicosis can be considered as having a low risk of thrombosis. During a quality of varicose vein surgery assessment project of the ANG (Association of German Vascular Surgeons in Private Practice), all patients were analysed for the necessity of administering an obligatory thrombosis prophylaxis with low molecular weight heparin. With 16,713 operations performed, 12 cases (0.072%) resulted in a certain deep venous thrombosis. The group with heparin-prophylaxis had a quota of 0.034% and the group without prophylaxis 0.093%. Statistically, the differences were not significant (p>0.05). In varicose vein surgery, obligatory postoperative administration of LWMH is not necessary. The individual risk to the patient must be considered. © Springer Medizin Verlag 2006.