Prostaglandin E ( 1 ) (PGE ( 1 ) ), the active ingredient of the drug alprostadil-alpha-cyclodextrin, has been effective in mitigating the clinical manifestations of peripheral arterial occlusive disease (PAOD). PGE ( 1 ) often is administered to patients with the potential for developing serious arrhythmias, presenting potential safety hazards if the drug caused or potentiated arrhythmias. However, PGE ( 1 ) has antiadrenergic properties and, theoretically, might have an antiarrhythmic action. Therefore, the effect of PGE ( 1 ) on frequency and severity of atrial and ventricular arrhythmias was evaluated from 48-hour electrocardiographic recordings in patients receiving PGE ( 1 ) therapy for severe PAOD. No significant effects on arrhythmia frequency or severity, and no evidence of proarrhythmia, was apparent after PGE ( 1 ) administration.