Abstract: An instrument for removing an obstruction in an internal body channel comprises an elongated catheter body adapted for insertion into a body channel having a first lumen throughout its length. An elongated guide and laser transmission conduit extends through the lumen of said catheter body and is movable therein so that its distal end can be extendable beyond the distal end of the catheter body. The proximal end of the movable conduit is connected to a controlled source of laser energy. A treatment element is provided at the distal end of the catheter body for further reducing the channel obstruction following preliminary penetration thereof by the movable laser transmission conduit. The treatment element may be a fixed laser transmission conduit which terminates at the end of the catheter body or a dilation balloon near its distal end.