Between 1992 and 2003, a total of 2029 aneurysms in 1748 patients were treated by endovascular occlusion with electrolytically detachable coils. In this series, electrolytically detachable platinum coils with Nylon fibers (Sapphire Detachable Coil System, MTI, Irvine, CA, USA) were used in 474 aneurysms solely or in combination with bare coils from various manufacturers. To determine the safety and clinical efficacy of Nylon fibered coils for the endovascular treatment of intracranial aneurysms in comparison to bare platinum coils a thorough retrospective statistical analysis by means of logistic regression and matched pairs analysis was performed. Only treatments with data for all matching variables were used, resulting in 421 matched pairs. The analysis was performed with respect to clinical status and numerous parameters concerning individual aneurysm characteristics (e.g., location, neck width, fundus diameter). Treatment-related parameters included the use and percentage of fibered coils, occlusion rate, procedural complications, early clinical outcome and Glasgow Outcome Scale (GOS) scores. Finally, long-term follow-up results (particularly recurrence, cause of recurrence and post treatment haemorrhage) were evaluated. Both logistic regression and matched pairs analysis showed a statistically improved occlusion rate if fibered coils had been used (96% largely occluded with the use of fibered coils vs. 84-85% with the exclusive use of bare coils). However, the amount of fibered coils calculated as percentage of coil length did not seem to have significant impact. Procedures with fibered coils did not lead to a higher rate of thromboembolic events (8.0% for fibered vs. 10.5% for bare coils).The apparently better clinical outcome in the group treated with fibered coils determined by both postprocedural outcome and GOS, did not reach statistical significance. Analysis of the anatomical properties showed no differences between the groups treated with bare and fibered coils in terms of neck width, fundus diameter, and anatomic location. As expected, a higher occlusion rate was achieved in aneurysms with smaller neck and fundus independent from the type of coil used. On follow up angiography, there was an apparently lower rate of recurrence secondary to coil compaction in the group treated with fibered coils, but these data were compromised by the fact that up to date only about one third of 474 aneurysms treated with fibered coils had undergone angiographic follow-up and this did not reach statistical significance. From our experiences, we conclude that the use of fibered electrolytically detachable platinum coils in aneurysm treatment leads to significantly improved occlusion rates compared to the sole use of bare platinum coils. We hope that with increasing follow-up data we will be able to confirm that the apparently reduced recurrence rates for aneurysms treated with fibered coils can be proven with statistical significance.