Three cases of perinatal paroxysmal supraventricular tachycardia are described. In two patients the tachycardia was present prior to delivery; in the third baby, who also had the Wolf-Parkinson-White Syndrome, the time of onset of tachycardia is not known. The risks of this condition to the foetus are largely unknown but severe intra-uterine cardiac failure can occur. Possible lines of management are discussed.