Treatment of gout and hyperuricemia can be difficult in patients with chronic renal failure. At present, there is no study available comparing the efficacy of the most widely used agent, allopurinol, and the uricosuric benzbromarone for the control of hyperuricemia in patients with renal insufficiency. We describe an open, randomized, actively controlled, comparative trial in patients with clearance of creatinine from 20 to 80 mL/ min/1.73 m(2). Patients were randomized to take benzbromarone (100-200 mg/day) or allopurinol (100-300 mg/day). Outcome variables were the following: reduction of serum urate (Sur), Sur & tl; 6 mg/dL (357 micromol/L), reduction of gouty bouts and reduction of tophi. During 9-24 months of follow-up 36 patients were studied.The reduction of Sur was higher with benzbromarone, and only 1 of 17 patients taking benzbromarone did not achieve Sur < 6 mg/dL versus 7 of 19 taking allopurinol. Patients who did not reach optimal Sur levels with allopurinol were more frequently taking diuretics and showed lower fractional excretion of urate and higher initial Sur levels than patients with proper control of Sur. Seven patients with suboptimal control of serum urate were changed to benzbromarone 100 mg/day, which showed efficacy similar in those who were initially randomized to benzbromarone. A reduction of gouty bouts and size of tophi was observed after proper control of Sur. Allopurinol is effective in controlling hyperuricemia, but patients with higher initial Sur levels or taking concomitant diuretic therapy are less prone to reach therapeutic goals.Benzbromarone is useful for the control of hyperuricemia in patients with renal insufficiency even with concomitant diuretic administration; patients benefited include those who previously had no improvement by taking allopurinol.