Guglielmi detachable endovascular coils were evaluated for magnetic resonance (MR) compatability at 1.5 T. Tests to determine magnetic field attraction (deflection angle and Petri-dish displacement methods), heating (infrared thermometry), and artifact production (beef phantom) were performed. Adverse event data were reviewed for MR imaging in 142 patients in whom the coils were implanted to treat intracranial aneurysms. There was no magnetic field attraction, the temperature increased 0.2 degrees C, and only a mild signal void relative to the size and shape of the coil was produced. All patients underwent MR imaging without incident. The Guglielmi coils are compatible with MR imaging at static magnetic field strengths of 1.5 T or less.