To investigate the prevalence of acute psychological disturbances during the 24 hours preceding life-threatening ventricular arrhythmias, we studied the mental states and psychological experiences preceding arrhythmic episodes in 117 patients who were referred for antiarrhythmic management. Sixty-two had survived cardiac arrest and 55 suffered symptomatic ventricular tachycardia. Twenty-five patients were experiencing acute emotional disturbances during the 24 hours preceding the arrhythmias. Eighteen had two or more episodes associated with psychological disturbances. These 25 patients were distinguished from the rest of the series in having generally less severe structural heart disease.