Inclusion Criteria:

1. Patient is between 18 and 80 years of age (inclusive).
2. Patient has a documented untreated intracranial saccular aneurysm 4-20 mm diameter angiographic lumen, ruptured or unruptured, suitable for embolization with coils.
3. Both GDC® Coils and Matrix 2® Coils (Every attempt should be made to treat with as much randomized coil type as possible to achieve optimal occlusion.) are treatment options (all shapes allowed with exception of GDC VortX Coil).
4. Target aneurysm can be adequately coiled at index procedure (NO staged coiling procedures). If a Neuroform stent is to be placed during a separate preliminary procedure, then screening and enrollment for the coiling procedure must take place after the stenting procedure is completed.
5. Target aneurysm morphology allows for adequate retention of coils within the aneurysmal sac without occlusion of the parent artery, as determined by the treating physician.
6. Patient (or patient's legally authorized representative for centers in the United States) has provided written informed consent.
7. Patient is willing and able to comply with protocol follow-up requirements.

Exclusion Criteria:

1. Patient is < 18 or > 80 years old.
2. Target aneurysm is not saccular in nature (mycotic, fusiform, dissecting).
3. Target aneurysm is > 20 mm maximum luminal dimension, < 4 mm maximum luminal dimension.
4. Target aneurysm has been previously treated by surgery or endovascular therapy.
5. Target aneurysm is in the physician's estimation unlikely to be successfully treated by endovascular techniques.
6. Patient presents as Hunt and Hess grade IV or V for a ruptured aneurysm.
7. Patient presents with Modified Rankin Score 4 or 5 at baseline.
8. Patient is concurrently enrolled in another investigational drug or device study unless permission is granted by the sponsor.
9. Patient has known hypersensitivity to Polyglycolic Polylactic Acid (PGLA), platinum, nickel, stainless steel or structurally related compounds found in Matrix 2® Coils and/or GDC® Coils.
10. Patients who have had or could have a severe reaction to contrast agents that cannot be adequately pre-medicated prior to the coiling procedure.
11. Patients who are unable to complete scheduled follow up assessments at the enrolling center due to limited life expectancy (< 12 months), comorbidities or geographical considerations.
12. Planned use of adjunctive therapy stents except Neuroform is not allowed.
13. Patients with Moya-Moya disease, AVMs, AV fistula, intracranial tumors, intracranial hematoma (unrelated to target aneurysm), significant atherosclerotic stenosis, tortuousity or other conditions preventing access to the target aneurysm.
14. Patients with multiple aneurysms.
15. Target aneurysm with significant thrombosis that may increase the likelihood of recanalization at the discretion of the investigator.
16. Female patient has a positive pregnancy assessment at baseline.