The risk of haematoma formation in the spinal canal following spinal or epidural anaesthesia given in the presence of s.c. heparin-dihydroergotamine (DHE) for prevention of postoperative thromboembolic complications was examined. The data were obtained from a study that compared the effectiveness of s.c. heparin-DHE and i.v. Dextran 70. Heparin-DHE was administered two hours before anaesthesia and surgery and during the postoperative course. All patients underwent elective or emergency operations of the musculo-skeletal system. The s.c. heparin-DHE group consisted of 187 patients operated under spinal (82 patients) or epidural (105 patients, 66 of whom received an epidural catheter) anaesthesia. There were no clinical signs to suggest the presence of an epidural haematoma nor were there any neurological symptoms. The same was true in the dextran group. Specific neurological examinations were not carried out, but the clinical results were controlled by means of a questionnaire filled out by the patients 6 weeks postoperatively. We conclude that s.c. heparin-DHE or i.v. dextran 70 has been used safely in the presence of spinal or epidural anaesthesia in these patients.