Most patients with a history of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) are at high risk of recurrence. Implanted defibrillators (ICDs) are highly effective in sensing and converting VT or VF to a perfusing rhythm. "Conventional" antiarrhythmic agents, which primarily block cardiac sodium channels, are relatively ineffective in preventing arrhythmia recurrence; amiodarone and sotalol appear to be effective in reducing recurrence and mortality rates, although the extent of benefit is not well understood. Despite the apparent advantage of ICDs, they have short- and long-term complications, are costly, and their benefit in prolonging the quantity or quality of life remains unproven. Randomized clinical trials which compare the effect of ICDs with that of antiarrhythmic drugs on mortality, cost, and quality of life will be necessary to understand how patients with malignant arrhythmias ought to be treated. If an ICD is implanted, adjunctive therapies need to be considered to treat the underlying heart disease and to derive optimum benefit from the device. Drugs may have beneficial or adverse interactions with devices, and the full understanding of these interactions requires further study.