Spinal or intracranial haematoma is a rare but severe complication of spinal/epidural anaesthesia with an incidence of less than 1:100,000. Coagulation defects, traumatic puncture, and anticoagulant drugs are assumed to be risk factors for the development of this kind of haematoma. Whether the risk of bleeding after spinal/epidural anaesthesia is increased by the administration of low-dose heparin (unfractionated or fractionated) for thromboprophylaxis is currently under discussion. RESULTS A randomised, prospective trial answering this question is not feasible because of the rarity of the complication. As an alternative, we identified all case reports described in the literature to date and analysed them for possible risk factors. In conjunction with spinal/epidural anaesthesia, we found 4 cases of spinal and 2 cases of intracranial haematoma following treatment with unfractionated heparin and 6 cases of spinal haematoma following treatment with different low-molecular-weight (LMW) heparins. In none of these cases could thromboprophylaxis with heparin be identified as the only risk factor for bleeding: in 11 of the 12 cases a difficult or traumatic puncture was described. Eleven patients showed three or more possible risk factors, e.g., coagulation defects, concomitant therapy with other anticoagulant drugs, or anatomic abnormalities. CONCLUSIONS We suggest that the development of spinal or intracranial haematoma after spinal/epidural anaesthesia is a multifactorial event. An influence of low-dose heparin prophylaxis as a cofactor cannot wholly be excluded because of the difficulty of studying the problem in a prospective way. The few case reports have to be seen in the context of millions of patients who have received either unfractionated or LMW heparin and lumbar or thoracic regional anaesthesia without any complication. We conclude that low-dose heparin prophylaxis (fractionated or unfractionated) is not a definite contraindication to spinal/epidural anaesthesia. High-risk (ASA III/IV) patients in particular benefit from effective postoperative analgesia achieved by local anaesthetics in combination with effective heparin thromboprophylaxis. Nevertheless, the absolute contraindications for regional anaesthesia must be respected and an individual risk/benefit analysis should be performed for every patient. An adequate time interval between application of heparin and regional anaesthesia or removal of a spinal/epidural catheter, atraumatic puncture technique, and careful neurologic monitoring during the post-operative period can minimise the risk of complications.