Abstract: A pusher-vasoocclusive coil assembly that is advanced through a catheter to a site within a vessel and is manipulated to detach the coil from the assembly. The coil has an enlarged member at its proximal end and the pusher has a keyway at its distal end that receives the enlarged member in interlocking engagement. The pusher and coil are coupled by placing the enlarged member in the keyway and enclosing the coupled assembly with a coaxial sleeve. The coil-pusher-sleeve assembly is positioned at the site and the sleeve is retracted to allow the member to move out of the keyway to uncouple the pusher and coil.