The occurrence of deep vein thrombosis (DVT) was studied by the 125-I-fibrinogen uptake test in 38 patients subjected to retropubic prostatectomy. The patients were randomly allocated to two groups: continuous lumbar epidural analgesia for up to 24 hours and general anaesthesia with intermittent positive pressure ventilation. Two of the 17 patients in the epidural group (12%) developed DVT in contrast 11 of the 21 patients in the general anaesthetic group (51%). The difference between the groups was significant. It is concluded that epidural analgesia offers a protection against postoperative DVT and is worth further investigation.