We examined 535 central venous catheterizations performed in a neonatal intensive care unit. A total of 273 catheters were positioned using intra-atrial ECG monitoring. With an average indwelling time of 23 days, we noted one complication for every 153 indwelling catheter days. A diagnosis of sepsis was confirmed on 22 occasions (4.1%). Sepsis occurred more often in infants with a birth weight < 1000 g (6.9%) compared with infants > 1000 g (3.1%). The risk of phlebitis was highest when the saphenous vein was used as the puncture site. The lowest risk of phlebitis was when the basilic vein was chosen. Five cases of thrombosis, two of myocardial perforation and one intravascular catheter breakage were registered. Catheter placement under ECG monitoring proved to be a very suitable method for reducing the incidence of malpositioning. There were no side effects specific to the ECG method. The ECG method can be used safely and makes radiological control usually unnecessary.