Abstract: An embolization device comprising an elongate coil having a plurality of turns formed of a metal which is relatively opaque to x-rays and having rounded ends. A group of fibers is provided. The group of fibers has an intermediate portion and first and second end portions. The intermediate portion is looped about one of the turns to form a loop on one of said turns. The end portions extend interiorly of the coil and outwardly of the coil through two adjacent turns adjacent the turn about which the loop is formed. The ends of the fibers of the end portions of each group are free to move. The group of fibers is free of knots. The loop serves as the sole means for retaining the group of fibers on the coil.