Central venous catheters are being increasingly used in both intensive care units and general wards. Their use is associated with both mechanical and infectious complications. This review will focus on short- and medium-term mechanical complications of catheter placement; infectious complications will be discussed in a separate article. The most important risk factors are patient characteristics (morbidity, underlying disease and local anatomy), the expertise of the doctor performing the procedure, and nursing care. Placement aids, such as ultrasound-guided catheter insertion, are also discussed.