The present invention relates to a multi-function catheter assembly for treating arterial plaques. The multifunction catheter comprises a flexible tubular catheter body, an inflatable balloon assembly capable of multi-stage inflation at a distal end of the catheter body, at least one fluid delivery conduit formed on the catheter body, and at least one balloon control conduit formed within the catheter body. The balloon, when inflated to a first stage inside a vessel at the treatment site, defines a chamber between the balloon and the vessel wall. The at least one fluid delivery conduit is adapted to permit the delivery of an agent into the chamber to dissolve a plaque. After the removal of the plaque, the balloon is further inflated to a second stage to install a stent in the space that is vacated by the plaque. The stent can be a pre-manufactured stent or a customized stent formed by filing the space between the balloon and the treated vessel wall with a fluent composition that is solidified in situ. The multi-function catheter may also be used for sealing off aneurysms, dilating vessel passages, and treating tumors and trauma.