Although fluoxetine has been shown to be both efficacious and well tolerated, few data are available on the use of this drug in patients with preexisting heart disease and in the elderly. The authors report a case of an elderly patient in whom atrial fibrillation and bradycardia developed shortly after she began treatment with fluoxetine. The dysrhythmias recurred on rechallenge with the drug. A review of the pertinent literature is presented and possible pathophysiologic mechanisms are discussed.