We report on an asymptomatic 2 1/4 year old girl. Echocardiography revealed cor triatriatum with a membrane separating the left atrium. Transesophageal echocardiography demonstrated 3 large perforations of the intraatrial membrane. Using Doppler sonography, no pressure gradients across these orifices were identified. Obstruction of the intraatrial membrane and pulmonary hypertension were excluded by cardiac catheterization. We therefore decided against surgical resection of the membrane and to follow the patient noninvasively by echocardiography. Follow-up over 18 months revealed no development of an obstruction across the intraatrial membrane. Our case shows that immediate surgical correction is not necessary in all patients with cor triatriatum. Conservative management of these patients requires full evaluation of the hemodynamics and careful follow-up examinations by echocardiography.