Abstract: A catheter device for transferring fluid material to or from one or more selected-length segment of a vessel. The device includes first and second catheters, each having a tube with distal and proximal ends, an inflatable balloon carried on the tube, adjacent the distal tube end, and a fluid conduit for supplying the balloon, with such operatively positioned in the vessel. A central region of the second-catheter tube is axially shiftable within the first-catheter tube, allowing the balloons to be placed at desired relative positions in the vessel. Fluid is injected into the region between the two balloons through a fluid passageway formed in a channel in the first-catheter tube.