This is a prospective, multi-center study of patients with intracranial or peripheral aneurysms who are treated by the PC 400 System. The primary objective is to gather post market data on the Penumbra Coil 400 (PC 400) System in the acute treatment of intracranial and peripheral aneurysms. Approximately 2,000 patients with intracranial or peripheral aneurysms treated by the PC 400 System at up to 100 centers will be enrolled. Data for each patient are collected up to discharge or 3 days post-procedure, whichever occurs sooner. Long term follow-up to one year will be conducted in accordance to the standard of care at each participating hospital.