Described here are devices, systems, and methods for applying pulsed or modulated electric fields to tissue. In some variations, a device may comprise a first elongate body comprising a lumen, a second elongate body at least partially positioned within the lumen, and an expandable member rolled about the second elongate body. The expandable member may comprise an inner end coupled to the second elongate body, an outer end coupled to the first elongate body, and an electrode array.