A method of extravasated delivery of a therapeutic and/or diagnostic agent to tissue is provided including inserting a catheter with a first balloon, a second balloon and a third balloon into a bodily cavity, inflating the first and second balloons by supplying fluid thereto to create a chamber, delivering the agent to the chamber, and increasing fluid pressure within the chamber by inflating the third balloon to facilitate extravasation of the agent into tissue. A multi-balloon catheter system is also provided including a catheter having a first balloon, a second balloon and a third balloon, and a fluid source that inflates the first and second balloons by supplying fluid thereto to create a chamber, wherein the catheter includes a fluid pathway for delivering the agent, and the fluid source increases fluid pressure within the chamber by supplying fluid to the third balloon such that the agent is extravasated into tissue.
