We describe the development, in three days, of a pediculate mass hanging on the right atrial lateral wall in a 39-year-old woman with a subclavian venous catheterization. She was a current smoker and alcoholic but without drug addict. The hypothesis of a non valvular right atrial infective endocarditis was considered at first, but subsequent events directed the diagnosis towards a thrombus, which was resorbed by heparin. We discuss the incidence, the complications, the treatment and the differential diagnosis of thrombus caused by a central venous catheter. The prevention of right atrial thrombus caused by a central venous catheter depends on the position of the central venous catheter tip, either in the superior vena cava or at the superior vena cava-right atrium junction. A more distal position is a frequent source of thrombotic and embolic complications.