Growing numbers of patients are treated with hemostasis altering drugs, as thromboembolic diseases are a major cause of mortality in our western society. The insertion of epidural or subarachnoidal needles and/or catheters in such patients carries the inherent risk of the development of a compressing vertebral canal hematoma. This is especially true in patients treated with thrombolytic agents or oral anticoagulants. Extreme caution is also warranted in patients treated with newer compounds as the thienopyridines, glycoprotein IIb/IIIa receptor antagonists, heparinoids, selective factor Xa inhibitors, and direct thrombin inhibitors. The available data do not allow making firm recommendations on the safe use of major neuraxial blocks. In contrast, the isolated use of acetyl-salicylic acid or non-steroidal anti-inflammatory drugs is no longer considered contraindicated, but their combination with of heparin remains controversial. Intraoperative heparinization, perioperative thromboprophylactic use of unfractionated heparin or low molecular weight heparins are possible if: 1) a minimum time interval between the regional anesthetic block and the administration of the previous or next dose of anticoagulant is respected and; 2) the specified dose limitations of the heparin compound used are not exceeded; and 3) indwelling catheters are removed only after the disappearance of any remaining anticoagulant effect.