A vasoocclusive embolic device deployment system for use in placing an embolic device at a preselected site within a vessel. The system comprises an elongated flexible delivery catheter having proximal and distal sections and a lumen extending therethrough an elongated flexible deployment catheter having proximal and distal sections and a lumen extending therethrough and being slidably disposed within the lumen of the elongated flexible delivery catheter an embolic coil having proximal and distal ends and a lumen extending therethrough a stretch resistant fiber having periodic undulations along at least a portion of the length of the fiber interspersed between straight portions and having proximal and distal ends, said stretch resistant fiber extending through the lumen of the embolic coil, said distal end of said stretch resistant fiber being attached to the distal end of the embolic coil, said proximal end of said stretch resistant fiber being attached to the proximal end of the embolic coil a headpiece mounted on the proximal end of the embolic coil and being disposed in a fluid tight engagement within the lumen of the distal section of the deployment catheter and, a source of fluid pressure coupled to the proximal section of the deployment catheter for applying a fluid pressure to the lumen of said deployment catheter for releasing the embolic coil from the deployment catheter.
