Isotopic angiocardiography was performed in 60 patients with proven congenital left-to-right shunt. A 99mTc labeled bolus was injected in a peripheral vein, and the first passage in the heart cavities was studied. Time-activity curves of the cardiac chambers were analysed, using a scintillation camera and a data processing system. In our study, we were able to confirm the presence of the shunt in 77% of the cases in which the radioactive bolus arrived well grouped in the vena cava. Quantitative results however remain imprecise. Isotopic angiocardiography indications are compared to radiologic angiocardiography and to right heart catheterism indications. Use of this non invasive technique could render more aggressive examinations unnecessary.