The aim of this study was to compare the total dose of intravenous pethidine required to give satisfactory analgesia to patients with acute renal colic between two groups, one of which was also administered rectal indomethacin on presentation and one which was not. This was a prospective, randomized, unblinded comparison study. Each group contained 39 patients. Group 1 received rectal indomethacin 100 mg and intravenous pethidine in 25 mg increments until pain was satisfactorily relieved. Group 2 received increments of intravenous pethidine alone. The primary endpoint was total pethidine dose required to achieve analgesia to the patient's satisfaction. No significant difference in total pethidine dose between the groups was found. It was concluded that administration of rectal indomethacin does not reduce the total dose of intravenous pethidine required to relieve the pain of acute renal colic.