To prove the efficacy of colchicine in the prevention of recurrences of acute pericarditis, 5 patients, age 24 to 64 years (mean 36), were treated during 18 months with 1 milligram daily. Previous treatment with steroids and/or non steroid antiinflammatory agents did not prevent 2-3 recurrences per patient, and was discontinued after entry into the study. There where no further recurrences of acute pericardial episodes during the 24 months of follow-up, and no side effects related to the treatment with colchicine were reported. We conclude that colchicine is effective in preventing the recurrences of acute idiopathic pericarditis.