We have performed the first controlled study of colchicine in acute gout, to determine its efficacy and toxicity, and to define the natural history of acute gout. Two-thirds of colchicine-treated patients improved after 48 hours, but only one-third of the patients receiving placebo demonstrated similar improvement. The colchicine-treated patients responded earlier; significant differences from placebo were shown after 18-30 hours. All patients given colchicine developed diarrhea after a median time of 24 hours (mean dose of colchicine 6.7 mg). This side effect occurred before relief of pain in most patients.