Haemorrhoidectomy is frequently associated with postoperative pain and prolonged hospital stay. A new technique of haemorrhoidectomy using the Ligasure device suited to day-case surgery is described. This technique was compared with conventional open diathermy haemorrhoidectomy. Forty patients with grade III or IV haemorrhoids were randomized to Ligasure (group 1) or conventional diathermy (group 2) haemorrhoidectomy. Operative details were recorded and patients recorded daily pain scores on a linear analogue scale. Follow-up was at 1, 3, 6 and 12 weeks to evaluate complications, return to normal activity, ongoing symptoms and patient satisfaction. Reduced intraoperative blood loss (median (range) 0 (0-5) ml versus 20 (12-22) ml; P < 0.001) and a shorter operating time (10 (8-11) versus 20 (18-25) min; P < 0.001) was observed in group 1 compared with group 2. More patients in group 1 were discharged on the day of operation (18 of 20 versus 11 of 20; P < 0.05) and there was a trend towards lower postoperative pain scores on day 1 (group 1 median 5 (95 per cent confidence interval (c.i.) 2.6 to 6.8) versus group 2 7 (95 per cent c.i. 4.2 to 7.7); P = 0.36). There was no difference between the two groups in the degree of patient satisfaction or number of postoperative complications. Ligasure diathermy may be used safely in the treatment of patients with grade III or IV haemorrhoids. It reduces intraoperative blood loss and operating time, and facilitates same-day discharge.