Cryoablation balloon catheters and methods are described herein. The cryoablation balloon catheter comprises a distal end section and an inflatable balloon member disposed along the distal end section for contacting a target tissue. The balloon member may be inflated with a thermally conductive liquid. One or more cooling microtubes are positioned within the balloon and a single phase liquid coolant is transported from a liquid source, through the microtubes to the distal section, and returned to a reservoir. Cryogenic energy is transferred from the microtubes, through the conductive liquid filling the balloon, through the wall of the balloon, and to the tissue. In a cryoablation balloon catheter, a plurality of flexible microtubes are adhered to a surface of the expandable balloon. Cryoenergy from the microtubes is directly transferred to the tissue.
