To determine the safety and effectiveness of ibutilide, we conducted a retrospective study of patients in a community hospital from December 1997-January 2000, reviewing hospital and pharmacy records for 12 inpatients (aged 68 ± 13 yrs) receiving ibutilide for atrial fibrillation or flutter. The cumulative conversion rate with ibutilide 0.012 ± 0.004 mg/kg was 58%. Serious cardiovascular adverse events were documented in six patients; of those patients, five had baseline QTc intervals above 440 msec, two experienced ventricular fibrillation, and four experienced symptomatic bradycardia (range 49-60 beats/minute) requiring medical intervention. The effectiveness of ibutilide was similar to that found in previous studies. However, more complications were seen in this setting where ibutilide was used infrequently and without stringent patient selection criteria or standardized administration protocols. To ensure optimal patient care, institutions should consider implementing guidelines or education strategies to reduce the potential for serious adverse effects associated with improper screening, dosing, and monitoring of patients receiving ibutilide.