A case of fetal supraventricular tachycardia which caused fetal hydrops was diagnosed at 29 weeks of gestation by fetal echocardiography. Transplacental fetal therapy with ma-ternal intravenous digoxin administration resulted in restoration of normal fetal sinus rhythm and disappearance of fetal hydrops on 7th day after initiation of treatment when the mat-ernal serum digoxin level was 2.11 ng/mL. The fetus showed normal sinus rhythm when evaluated by fetal echocardiography during the remainder of pregnancy with maternal oral digoxin maintenence. At birth, the infant did not show any cardiac arrhythmia and hydropic appearance.