BACKGROUND: During subclavian vein catheterization, a potential, but rare, hazard is the phrenic nerve injury, which compromises respiratory function. We conducted a cadaver study focused on the possible anatomical relationships between the subclavian vein and the phrenic nerve.METHODS: Forty-two adult cadavers (84 heminecks) were dissected. Special attention was given to the topography of the phrenic nerve and subclavian vein.RESULTS: In all but three cases (81 of 84), normal topography was present, that is, the nerve was posterior to the vein. In two cases, the phrenic nerve crossed anterior to the subclavian vein and in one case traversed the anterior wall of the subclavian vein.CONCLUSIONS: Variants of the relationship of the subclavian vein and the phrenic nerve should be familiar to anaesthesiologists during subclavian vein cannulation in order to achieve successful vein approach without causing phrenic nerve palsy.