Peroperative blood loss, arterial blood pressure and central venous pressure were studied in patients subjected to retropubic prostatectomy. The patients were randomly allocated to two groups, continuous lumbar epidural analgesia for up to 24 hours and a thiopentone-oxyg n-nitrous oxide-alcuronium-pethidine sequence with intermittent positive pressure ventilation. The mean peroperative blood loss during operations under epidural analgesia was significantly less than that under general anaesthesia (370 +/- 34 ml vs. 590 +/- 34 ml vs. 590 -/+ 35 ml, mean -/+ SE). Only one patient out of 17 cases of epidural analgesia needed a peroperative blood transfusion, in contrast to 5 out of 21 general anaesthesias. Both the arterial systolic and diastolic pressures, and central venous pressure were significantly lower under epidural analgesia than general anaesthesia. It was concluded that decreased arterial and venous pressure were responsible for the reduced blood loss under epidural analgesia.