Complications after the percutaneous insertion of central venous catheters are pneumothoraces, catheter-associated infections and thrombosis. In rare cases, late problems occur as a disruption of the main thoracic duct or vascular erosion. The developing pleural effusion must be analysed for other causes such as congestive heart disease, inflammatory or tumorous disease, pancreatitis, low blood protein, or subdiaphragmatic abscess. The following case report describes a rare catheter complication in a 16-year-old polytraumatised patient. The differentiation to a chylothorax and suitable therapy are described.