Incidental rupture of an internal carotid artery aneurysm complicating a CT-guided needle biopsy of the neck is reported. A contrast CT scan failed to diagnose the lesion, which was not pulsatile and thought to be a neoplastic cervical lymph node. After leakage of the aneurysm. Color-Doppler scan and MRI identified aneurysmal changes of the carotid artery wall with an intraluminal thrombus. Successful emergency resection with a PTFE interposition graft was performed.