BACKGROUND Bioactive polyglycolic/polylactic acid (PGLA)-coated Matrix detachable coils were reported to incite intra-aneurysmal inflammation and fibrosis. Multiple large case series with Matrix-1 coils have shown no advantage with respect to aneurysm recurrence. Second-generation Matrix-2 coils were designed with improved platinum support and reduced copolymer friction. We assessed the safety and efficacy of Matrix-2 coil embolization. METHODS 84 aneurysms were embolized primarily with Matrix-2 coils. Anatomic results were evaluated using a modified Raymond scale with progressive occlusion or recanalization/recurrence strictly defined as any interval change in intra-aneurysmal opacification. RESULTS Mid-term (8.9 ± 3.4 months) and long-term (23.0 ± 7.4 months) follow-up was available for 65 aneurysms. At mid-term, 55 (85%) aneurysms remained stable (or progressed to occlusion) versus 10 (15%) recurrent aneurysms, 7 (11%) requiring retreatment. At long term, 49 (75%) aneurysms remained stable versus 16 (25%) recurrent aneurysms, 12 (18%) requiring retreatment. Statistically significant factors affecting recanalization included ruptured aneurysms 9/20 (45%), large aneurysms 5/8 (71%), post-procedure residual aneurysms 6/12 (50%) and differential coil packing density of recurrent (21%) versus stable (28%) aneurysms. Patient morbidity (5%) was limited to thromboembolic complications (n=4) or aneurysm rerupture (n=1). Patient mortality (5%) was secondary to subarachnoid hemorrhage complications (n=4) with no procedure-related deaths (0%). CONCLUSIONS Coil embolization with Matrix-2 coils is safe and effective, preventing recanalization in small aneurysms at mid-term. Although these aneurysm recurrence rates initially appeared lower than previous reports with Matrix-1 or platinum coils, significant late recanalization was observed on long-term follow-up. We postulate that any derived benefit from Matrix-2 coils is directly dependent on post-procedure outcomes and coil packing density.