Background Traditionally, allopurinol is not initiated during an acute gout attack to avoid prolonging the painful arthritis. The 2012 American College of Rheumatology Guidelines for the Management of Gout suggest that urate-lowering therapy can be started during an acute attack, based on "consensus opinion of experts, case studies, or standard of care." Objective The aim of this study was to determine whether initiating allopurinol will adversely affect the resolution of acute, treated gout. Methods We conducted a 28-day, placebo-controlled, double-blind study of allopurinol initiation in patients with acute gout. Patients with crystal-proven gout by arthrocentesis were enrolled if they presented to the rheumatology clinic with an acute gout attack within 72 hours from initial therapy. The patients were also required to meet at least 1 additional criterion for urate-lowering therapy including (1) the presence of gouty tophi, (2) more than 1 acute gout attack per year, (3) a history of nephrolithiasis, or (4) urate overproduction (>1000 mg in 24-hour urine collection). Patients were excluded from the study if they had a glomerular filtration rate of less than 50 or liver function test of greater than 1.25 times the upper limit of normal. The treating physician determined therapy for the acute gout attack. Standard prophylaxis, with colchicine or nonsteroidal anti-inflammatory drugs, was prescribed. Allopurinol or placebo was initiated at 100 mg daily for the first 14 days and then increased to 200 mg daily for the next 14 days. The primary end point was protocol defined days to resolution of acute gout, incorporating patient-rated joint pain and physician examination. Secondary measures included Physician Global Assessment, patient-rated pain, adverse effects of therapy, and serum uric acid. Results Thirty-one patients (17 on placebo, 14 on allopurinol) completed the study. Both intent-to-treat and completer analyses showed only a statistically insignificant difference in days to resolution (15.4 days in the allopurinol group completers vs 13.4 days in the placebo group; P = 0.5). The secondary measures revealed that the acute phase of pain rapidly improved in both groups. Conclusions We initiated allopurinol at low doses during an acute gout attack in patients who met criteria for starting urate-lowering therapy and did not have abnormal kidney or liver function. In this cohort, allopurinol did not prolong the acute, treated attack.