BACKGROUND AND OBJECTIVES: Cannulation of a central vein is an everyday procedure in anaesthesiology. However, anatomical variations of the size and/or location of the internal jugular vein might prevent cannulation, while repeated efforts might lead to severe complications. The aim of this retrospective study was to explore anatomical abnormalities of the internal jugular vein with regard to diameter of the vein's lumen and to define their clinical significance.METHODS: The cervical regions of 93 cadavers, 186 sides in total, were dissected and the anatomical variations of internal jugular vein diameters in relation to the external jugular vein and to the common carotid artery were recorded and photographed.RESULTS: The diameter of the veins in three cases were less than 6 mm, while ipsilateral external jugular veins were larger than average (3/93).CONCLUSIONS: Anatomical variations of the internal jugular veins are clinically significant, especially in cases where venous access is important.