Catheter-related venous thrombosis is one of the most important complications of central venous catheters. The aim of this prospective study was to assess the risk factors that may be important in the development of catheter-related thrombosis. Multiple lumen (n = 20) and single lumen (n = 24) polyurethane catheters were inserted to the subclavian vein by the infraclavicular approach in 44 consecutive patients. All variables that may be significant for the development of thrombosis related to the patient, the catheter, the insertion technique and the solution administered through the line were recorded. Eighteen of 44 patients (40%) were found to have venous thrombosis. Two factors were found to correlate significantly with the development of central venous catheter-related thrombosis, namely the number of vein punctures (one vs two punctures, P < 0.01) and the composition of solution (fluid replacement vs total parenteral nutrition, P = 0.01).