A cryogenic tissue ablation instrument, comprising: an elongate flexible body having a proximal supply port adapted for coupling with a source of pressurized flowable coolant, and a supply lumen in fluid communication with the proximal supply port and extending through the elongate body to a distal portion thereof; a dispersion member coupled to or formed out of the distal portion of the elongate body, the dispersion member including an interior lumen in fluid communication with or otherwise comprising a portion of the supply lumen; and an expandable balloon carried on the distal portion of the elongate body and having a wall, an interior surface of the wall defining an interior of the balloon, the dispersion member at least partially extending into the balloon interior and having a plurality of coolant dispersion apertures in fluid communication with the respective supply lumen and balloon interior, wherein the coolant dispersion apertures are sized and located on the dispersion member such that a pressurized flowable coolant provided in the supply lumen will enter the balloon interior through the dispersion apertures in the form of a liquid spray that contacts and provides substantially uniform cooling of the interior wall surface of a treatment region of the balloon. wherein the dispersion apertures comprising a first plurality of circumferentially spaced coolant dispersion apertures, and a second plurality of circumferentially spaced coolant dispersion apertures located distally on the dispersion member from the first plurality, wherein apertures of the second plurality are offset circumferentially with respect to the apertures of the first plurality, characterized by the coolant dispersion apertures formed out of flaps cut into the dispersion member, herein the most distal edge of each flap remains attached to the dispersion member and the proximal flap end is depressed into the supply lumen for dispersing coolant flowing in the supply lumen into the balloon interior, an elongate flexible body having a proximal supply port adapted for coupling with a source of pressurized flowable coolant, and a supply lumen in fluid communication with the proximal supply port and extending through the elongate body to a distal portion thereof; a dispersion member coupled to or formed out of the distal portion of the elongate body, the dispersion member including an interior lumen in fluid communication with or otherwise comprising a portion of the supply lumen; and an expandable balloon carried on the distal portion of the elongate body and having a wall, an interior surface of the wall defining an interior of the balloon, the dispersion member at least partially extending into the balloon interior and having a plurality of coolant dispersion apertures in fluid communication with the respective supply lumen and balloon interior, wherein the coolant dispersion apertures are sized and located on the dispersion member such that a pressurized flowable coolant provided in the supply lumen will enter the balloon interior through the dispersion apertures in the form of a liquid spray that contacts and provides substantially uniform cooling of the interior wall surface of a treatment region of the balloon. wherein the dispersion apertures comprising a first plurality of circumferentially spaced coolant dispersion apertures, and a second plurality of circumferentially spaced coolant dispersion apertures located distally on the dispersion member from the first plurality, wherein apertures of the second plurality are offset circumferentially with respect to the apertures of the first plurality, characterized by the coolant dispersion apertures formed out of flaps cut into the dispersion member, herein the most distal edge of each flap remains attached to the dispersion member and the proximal flap end is depressed into the supply lumen for dispersing coolant flowing in the supply lumen into the balloon interior,