Endosaccular packing of inoperable aneurysms with electrolytic platinum coils was performed in 50 patients. Complete embolization of the aneurysms was achieved in 100% of small, 95% of large and 85% of giant aneurysms, with combined procedural and periprocedural morbidity and mortality rates of 6 and 4%, respectively. Follow-up angiography of 42 aneurysms demonstrated some degree of refilling in 17% of small, 19% of large and 50% of giant aneurysms. The risks associated with the procedure were similar in aneurysms of the carotid and vertebrobasilar circulations. This treatment should therefore be considered for all inoperable aneurysms and particularly for aneurysms involving the posterior circulation. Its long-term efficacy remains uncertain.