mass in the base of the left side of the neck. His left thyroid lobe had been resected for goiter 16 years ago. Ultrasonography revealed an aneurysm in the shape of a triangle in the transverse plane and ovoid shape in the saggital plane, 42 34 21 mm in size, closely attached to the lateral aspect of the internal jugular vein (IJV) (Panels A and B). At the junction of the middle and the distal third of this aneurysm, a communication with the IJV was seen, 6–7 mm in diameter. High-velocity blood flow was registered within the central part of the aneurysm, and much slower flow near the aneurysmal wall, causing a ‘pseudothrombosis’ effect. The flow through the aneurysmal neck was bidirectional and respiratory phase-dependent (Panel B). Surgery was performed with resection of the aneurysm and lateral suture of the jugular vein. No thrombus was found within the aneurysm, and there was no reaction in the surrounding tissue to connect the previous neck surgery with the aneurysm formation. Pathologic examination showed all layers of a normal vein, with endothelial continuity and fibroblastic proliferation and some mixed muscle layers. Jugular vein aneurysms are rarely seen,1,2 and most frequently have been described in children. They appear to have a benign natural history, and should be excised only if symptomatic, enlarging or disfiguring.3 Duplex 3D ultrasonography was a reliable technique for diagnosis and sufficient for surgical treatment of the problem.