It frequently happens in the course of complete heart block that attacks of syncope appear associated with standstill of the ventricles. These are the classical attacks known as the Adams-Stokes syndrome. It appears to be a fact that the severity of the attacks depends on the duration of the ventricular asystole. It has been reported1that the subcutaneous injection of epinephrin can do away with such attacks, but as the effect of epinephrin generally lasts a very short time, it does not seem likely that the recurrence of attacks is thus prevented. Epinephrin failed to prevent the reappearance of syncope in one of the cases reported here. However, no method has been proposed so far for dealing directly with these attacks in the sense of diminishing their frequency or preventing them. This has been accomplished in the following three cases by the oral administration of barium chlorid. The periods of