Double-pigtail stents are placed commonly in patients before extracorporeal shock wave lithotripsy to prevent ureteral obstruction from steinstrasse. The use of double-pigtail stents in lithotripsy patients with a moderate stone burden was studied in a prospective randomized trial. Patients with unilateral renal stone(s) with at least 1 diameter between 7 and 25 mm. were eligible for the study. Fifty patients were randomized to a control or stented group. Double-pigtail stents with an attached suture were placed immediately before extracorporeal shock wave lithotripsy in the stented group. Stents were removed by the patients 1 week after lithotripsy. A survey on pain and associated symptoms was completed by patients at 1 and 14 days after treatment. There was no statistical difference in flank or abdominal pain, nausea, vomiting, temperature or use of analgesics at 1 and 14 days after extracorporeal shock wave lithotripsy in the control and stented groups. All patients in the stented groups complained of side effects attributable to the stent including urinary frequency and urgency, bladder pain, hematuria and flank pain with urination. Of 25 patients with stents 7 (27%) had early removal because of severe irritation, early migration or accidental removal. Among the patients with followup x-rays 1 month after treatment 17 of 21 (81%) in the control group and 12 of 19 (63%) in the stented group showed no evidence of remaining stones. The use of double-pigtail stents is not beneficial in patients with a moderate stone burden. Double-pigtail stents are associated with considerable patient discomfort but no decrease in symptomatic ureteral obstruction or final stone eradication rate.