Apparatus (20) for carrying out a prophylactic or treatment procedure on tissue comprises a device (21) having a chamber (22) and at least one active element such as an electrode (23) within the chamber (22). The chamber (22) has an opening (26) through which tissue is drawn into the chamber (22). Means for drawing the tissue into the chamber may comprise a vacuum lumen with vacuum orifices (25) in the chamber (22). Treatment such as electroporation may be applied to tissue in the chamber (22).
