Propafenone is an effective antiarrhythmic drug used widely for the treatment of supraventricular and ventricular arrhythmias. Although it is generally well tolerated, 30 to 45% of patients may experience adverse cardiac effects. In 15 to 20% of patients, adverse effects may involve other organ systems. A wide variety of adverse central nervous system effects have been reported in association with propafenone; dizziness is the most common. Ataxia caused by propafenone has been reported to the pharmaceutical companies and drug monitoring agencies, but has not been well described or emphasized in the medical literature. We describe 3 elderly patients with moderate to severe ataxia that occurred while they were taking propafenone.