BACKGROUND AND PURPOSE: An infrequent occurrence during endovascular treatment is protusion of detachable coils into the parent lumen with a subsequent thrombosis within in the parent vessel or embolic events. We report the short- and intermediate-term angiographic and clinical outcomes of patients who experience coil or loop protrusions and are managed with medical or additional endovascular treatments. MATERIALS AND METHODS: The coil protrusions were identified by retrospective review of 256 consecutive patients treated at 3 centers with endovascular embolizations for intracranial aneurysms and subsequently categorized as grade I when a single loop or coil protruded into the parent vessel lumen less than half the parent artery diameter; grades II and III were assigned when a single coil or loop protruded more than half the parent artery diameter, respectively. RESULTS: There were 19 patients with grade I (n = 9), grade II (n = 4), or grade III (n = 6) coil protrusions. Patients with active hemodynamic compromise (n = 6) had intracranial stents placed in addition to aspirin (indefinitely) and clopidogrel (range, 1-12 months; mean, 4.5 months) treatment. The remaining patients were placed on aspirin indefinitely. Complete aneurysm obliteration was achieved in all patients except in 3 in whom near-complete obliteration was achieved. Two patients had intraprocedural aneurysm ruptures, both of whom survived hospitalization. There were 4 deaths (4-21 days), all due to major strokes in different vascular distributions related to vasospasm (unrelated to the coil protrusion). CONCLUSIONS: Management of coil protrusions with antiplatelet therapy and placement of stents (in selected patients) appears efficacious in preventing vessel thrombosis.