A case of chronic atrial tachycardia in a 12-year-old boy is reported. His complaints were frequent precordial palpitation and mild exertional dyspnea with 6 months duration, EKG showed the findings of chronic atrial tachycardia, repetitive type. Digitalis therapy was established and continued for about 6 months. The attack of tachycardia ceased from 2 weeks after beginning of the treatment and didn't reappeared until the end of treatment. After cessation of digitalis therapy, follow-up study was made for over 6 months but no attack of tachycardia was observed even during this period. A review of literatures was made briefly.