This study examined the frequency of atrioventricular (AV) dissociation and accelerated junctional rhythms in 59 patients receiving oral verapamil. Accelerated junctional rhythms and AV dissociation were frequent in patients with supraventricular tachyarrhythmias, particularly AV nodal reentry. Verapamil administration to these patients led to an asymptomatic increase in activity of these junctional pacemakers. In patients with various chest pain syndromes, verapamil neither increased the frequency of junctional rhythms nor suppressed their role as escape rhythms under physiologically appropriate circumstances.