Endocavitary electrocardiography was used during surgery on the posterior fossa and the cervical spine in semi sitting position as a check when placing a ventriculo atrial shunt while inserting an intracardiac catheter in hydrocephaly. The method was as follows: one of the metal electrodes usually employed in cardiology, was replaced by a water column by filling the catheter with a 20% saline solution. The catheter, which is inserted via a wide vein (e.g. the internal jugular vein) was pushed upwards cm by cm until in the superior vena cava and further mm by mm until in the right atrium. The patient was connected with the 4 electrodes of an electrocardioscope; subsequently, at the ECG recording, either the electrodes for the left arm, or the thoracic electrodes were connected with the metal extension piece of the syringe containing the 20% saline solution and attached to the endocavitary catheter. The morphological changes in the auriculogram, that could be followed on the electrocardioscope, allowed the determination of the exact localization of the catheter in the atrium at any moment during the moving of the catheter. Reading the auriculogram was simple, provided that some technical precautions were observed. The only obstacle in this method was formed by the patients having atrial fibrillation. The authors have abandoned the radiological control method in favour of the electrocardiographic control method, which, in their opinion, is the simplest, most correct and rapid method.SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe