The patient with recurrent malignant ventricular arrhythmias (ventricular fibrillation or ventricular tachycardia with syncope) presents a complex therapeutic problem. To examine this problem, a study was made of 43 consecutive patients with such arrhythmias (mean age 54 years for the 33 men and 43 years for the 10 women). Arrhythmias were not precipitated by either remediable clinical conditions or acute myocardial infarction. The population was divided into two nonrandomized groups based on the type of therapeutic intervention employed. The 26 patients in Group 1 (20 with ventricular fibrillation, 6 with ventricular tachycardia) were subjected to a systematic attempt to select two independently effective antiarrhythmic drugs. Acute drug testing was followed by drug usage over 48 to 72 hours with drug efficacy determined with use of ambulatory monitoring and exercise stress. The 17 patients in Group 2 (10 with ventricular fibrillation, 7 with ventricular tachycardia) received standard antiarrhythmic therapy based on clinical factors and "therapeutic" blood drug concentrations. Twenty-four of 26 patients in Group 1 (92 percent) demonstrated control of arrhythmias and are alive at a mean follow-up period of 17 months. Of 121 drug tests, 47 (39 percent) were effective, 58 (48 percent) were ineffective and 16 (13 percent) provoked major adverse effects. The most effective combination of drugs involved a beta adrenergic blocking agent, a cardiac glycoside and quinidine. Ten of 17 patients in Group 2 (59 percent) have died after a mean follow-up period of 14.8 months. Elements of a successful management program are outlined.