The suitability of spinal versus epidural blockade for transurethral resection of the prostate was studied in 60 patients randomly allocated to spinal and epidural anaesthesia groups. 0.5% bupivacaine (Marcain, Astra, Sweden) was injected at the L3-L4 interspace, the dose being 3 ml in the spinal group and 19 (16-25) ml in the epidural group. The blood pressure decreased similarly after both epidural and spinal injections, but the heart rate was not significantly altered. No statistically significant differences were found between the groups in any of the variables measured, including blood pressure, heart rate, intraoperative blood loss and per- and post-operative complications. However, altogether eight patients in the epidural group, but none in the spinal group, had to be treated because of hypotension (P less than 0.001). The main advantage of the spinal blockade was a faster and more reliable blockade of the lowest sacral segments, and the main advantage of the epidural blockade was a less pronounced and shorter duration of motor blockade.