Abstract: A method for surgical dissection, sizing and for expansion of a tissue pocket in a naturally occurring fascial cleft for use in plastic surgery applications and other applications where it is desirable to dissect an anatomically defined and bounded tissue pocket, determine the appropriate size of a prosthesis to be implanted into the tissue pocket and, if necessary, further expand the tissue overlying the tissue pocket. An inflatable device which performs the three distinct functions of dissection, sizing and tissue expansion is used. In a preferred method, a dissecting balloon device is tunneled bluntly to a desired location within a fascial cleft in the female breast. The device is then inflated to dissect tissue layers adjacent the fascial cleft until ligaments defining boundaries of the fascial cleft are reached, to create a tissue pocket extending to the ligamentous boundaries.