The authors describe the problem of spontaneous changes of the position of the catheter in venous vascuports with a cannula inserted via the vena subclavia or internal jugular vein into the vena cava superior, used most frequently for repeated administration of chemotherapy. The correct position of the catheter is important in the venous port system for the proper function of the whole system. During dislocation of the catheter the function is impaired to a varying extent and the number of inflammatory and thrombotic complications increases and dislocations beyond the venous system lead to extravasal administration of the drug. Possible diagnosis of this condition and subsequent correction of the position of the cannula is described in a 48-year old man who developed spontaneous dislocation of the position of the cannula from the vena cava superior into the internal jugular vein. Correction by means of a hook inserted via the ipsilateral femoral vein into the vena cava inferior and via the vena cava superior into the internal jugular vein was successful only temporarily. Because of repeated dislocation the port system was removed.