To assess the ability of ultrasonography to detect the tip of a very thin (0.4 mm outer diameter) percutaneous central venous catheter (PCVC) in neonates, the PCVC tip location was assessed by ultrasonography (US) and compared to the location estimated by standard radiography for 57 PCVCs in 44 neonates. Of 57 occasions, the examiner could not find the PCVC tip in three cases (5%). In the remaining 54 instances, in 87% of cases, the PCVC tip position was consistent with the location implied by skeletal landmarks on standard radiographs. On 24 occasions we also assessed catheter tip dislodgement according to flexion and extension of the infant's arm. US could detect 78% of cases of catheter tip dislodgement. The PCVC tip was sometimes visualized as a dot and parallel lines as well as mere parallel lines. In a large population of cases, US is a reliable method for detection of a thin PCVC tip. US provides precise information about the PCVC tip position in relation to vascular structure and contributes to safer positioning of the PCVC than traditional radiography alone.