The antiarrhythmic effects of 4 pteridine analogues, 2 of which are potassium‐sparing diuretics, triamterene (2, 4, 7‐triamino‐6‐phenylpteridine) and [2‐phenyl‐4, 7 diaminopteridine‐6‐(N‐diethylaminoethyl) carboxamide] and 2 of which have no diuretic effects [2‐phenyl‐4, 7‐diaminopteridine‐6‐(N‐2‐hydroxyethyl) carboxamide] and [2‐phenyl‐4, 7 diaminopteridine‐6‐(N‐dimethylaminopropyl) carboxamide], on ouabain‐induced ventricular tachycardia in intact pentobarbital‐anesthetized dogs were investigated. Ouabain was given as a continuous infusion 2 µg/kg/min intravenously until 5 min after the onset of a sustained ventricular tachycardia. It was found that both 6‐(N‐dimethylaminopropyl) and 6‐(N‐diethylaminoethyl) carboxamide derivates of the pteridine had a significant protective effect against ouabain‐induced ventricular tachycardia in dogs that had been pretreated with a dose of 5 mg/kg intravenously. At this dose the 2 pteridine compounds with diuretic activity exhibited a transient antiarrhythmic effect in abolishing the ouabain‐induced ventricular tachycardia while those without diuretic properties failed to suppress the ventricular tachycardia.