Background and Purpose -Endovascular coil embolization has become an accepted alternative for the treatment of intracranial aneurysms. The purpose of this st udy was to evaluate the clinical safety and the angiographic stability of aneury sm occlusion with a new class of biologically active platinum coils after a 6-m onth period. Methods -Twenty-five patients with 25 intracranial aneurysms were treated by selective embolization with a new coated bioactive coil (Matrix; Bos ton Scientific Neurovascular). Matrix coils were used alone in 6 patients and in combination with Guglielmi detachable coils (GDCs; Boston Scientific Neurovascu lar) in 19. Angiographic results, procedure-related complications, and adverse neurological events during the follow-up period were recorded. Magnetic resonan ce angiography was performed at 6 months in all patients. Results -Initial angi ographies demonstrated complete occlusion in 17 patients, residual neck in 7, an d a persisting aneurysm in 1. The clinical follow-up showed stable results in a ll patients. The grade of aneurysm occlusion at 6 months improved in 4 patients, remained stable in 15, and deteriorated in 6. Three patients needed retreatment because of a major aneurysm recanalization. Angiographic recurrences in cases o f aneurysms treated with a combination of Matrix coils and GDCs occurred within the expected range for bare platinum coils. Two of 3 patients needing retreatmen t had been treated with Matrix coils alone. Conclusion -Stable results were obt ained predominantly when Matrix coils were combined with bare platinum coils. A prospective, randomized study is necessary to assess the potential benefit of Ma trix coils for patients treated by endovascular techniques. Background and Purpose -Endovascular coil embolization has become an accepted alternative for the treatment of intracranial aneurysms. The purpose of this st udy was to evaluate the clinical safety and the angiographic stability of aneury sm occlusion with a new class of biologically active platinum coils after Methods-Twenty-five patients with 25 intracranial aneurysms were treated by selective embolization with a newly coated bioactive coil (Matrix; Bos ton Scientific Neurovascular). Matrix coils were used alone in 6 patients and in combination with Guglielmi detachable Magnetic resonance angiography was performed at 6 months in all patients. Results -Initial angi Theographies demonstrated complete occlusion in 17 patients, residual neck in 7, an da persisting aneurysm in 1. The clinica l follow-up showed stable results in a ll patients. The grade of aneurysm occlusion at 6 months improved in 4 patients, remained stable in 15, and deteriorated in 6. Three patients needed retreatment because of a major aneurysm recanalization. Angiographic recurrences in cases of aneurysms treated with a combination of Matrix coils and GDCs occurred within the expected range for bare platinum coils. Two of 3 patients needing retreatmen t had been treated with Matrix coils alone. Conclusion -Stable results were obt ained predominantly when Matrix coils were combined with A prospective, randomized study is necessary to assess the potential benefit of Ma trix coils for patients treated by endovascular techniques.