A catheter positioning system includes a catheter needle assembly comprising a catheter having a permanent hub and a needle carried in the catheter lumen. A releasable clamp is used to compress the catheter against the needle to prevent axial movement of one relative to the other. The clamp is periodically released after being moved a short distance toward the target vessel or nerve and is repositioned a short distance from the skin entry point to further advance the catheter needle assembly. The clamp is configured to be removed from the catheter by movement in a direction other than along the longitudinal axis of the catheter while the catheter hub remains in place. After successful placement of the catheter, the clamp may be snapped apart or opened along a hinge without moving the catheter from its final position.