The relative safety and efficacy of intravenous administration of adenosine, lignocaine, disopyramide, flecainide, and sotalol for termination of stable, induced ventricular tachycardia was assessed in serial trials. Ventricular tachycardia was terminated by pacing if it persisted 10-15 min after the end of drug administration. 24 patients with recurrent ventricular tachycardia were studied. Ventricular tachycardia was terminated by a drug in 35 of 105 trials. In 6 patients no drug terminated the arrhythmia. Adenosine did not terminate tachycardia or have any serious adverse effect in any patient; both flecainide and disopyramide were significantly more effective than lignocaine, but flecainide had significantly more severe adverse effects than lignocaine. Lignocaine was the safest drug and should continue to be used as first-line drug therapy for stable ventricular tachycardia. Disopyramide should be considered as second-line treatment. DC cardioversion is necessary for unstable ventricular tachycardia, and its availability must be ensured before attempted pharmacological intervention.