Abstract: A method and apparatus is provided for cryogenically ablating a predetermined portion of tissue in the body of a patient. Cryoablation is accomplished by a cryoblation catheter having a hollow shaft insertable into the blood vessel of a patient. The shaft has a closed tip portion and a fluid flow passage for directing a flow of cryogenic fluid to the tip. Cryogenic cooling is effected by a liquid-to-gas fluid phase change adjacent the catheter tip. Electrical signal activity may be monitored by an electrode formed integral with the tip to confirm treatment of the paper tissue site.