Abstract: An infusion catheter, for use in conjunction with a balloon dilatation catheter, comprises an elongate, flexible tube defining an infusion lumen, and an expansible infusion sleeve located near its distal end, the sleeve comprising an expansible network of spacer elements disposed between proximal and distal elastomeric sealing bands. When deployed at a treatment site in a blood vessel or other bodily passage, the elongate tube of the present invention concentrically surrounds the dilatation catheter, the infusion lumen being defined therebetween, with the infusion sleeve concentrically surrounding the balloon. The spacer elements of the expansible network create an axially-elongated, circumferential flow path or interstice between the balloon and the vessel wall when the balloon is inflated, the interstice being in fluid communication with the infusion lumen, through which a therapeutic fluid is delivered to the treatment site.