A radiofrequency surgical instrument, comprising: an end effector assembly including first and second jaw members (210,220) each defining a tissue-contacting portion, at least one of the first or second jaw members movable relative to the other between an open position and a closed position, wherein, in the closed position, the first and second tissue-contacting portions cooperate to define a grasping area therebetween, the first and second jaw members adapted to connect to a source of RF energy to conduct RF energy between the tissue-contacting portions and through tissue grasped within the grasping area to treat tissue, wherein the tissue-contacting portion of each of the first jaw member and the second jaw member defines a first opening (219,229) therethrough, the first opening disposed within the grasping area and in communication with a first lumen (118,128) defined at least partially through the first jaw member, the first lumen adapted to connect to a source of vacuum to enable aspiration through the first opening, the tissue-contacting portion defining a first tissue contacting surface (214,224), a second tissue-contacting surface (218,228), and a wall (217,227) disposed between the first and second tissue-contacting surfaces, wherein the first and second tissue-contacting surfaces are offset relative to one another via a step (216,226) and the first opening is defined through the wall, characterised in that the steps of the first and the second jaw member are laterally offset relative to one another such that in an aligned orientation of the jaw members, the second tissue-contacting surface portion of the first jaw member opposes the first-tissue contacting surface portion of the second jaw member. an end effector assembly including first and second jaw members (210,220) each defining a tissue-contacting portion, at least one of the first or second jaw members movable relative to the other between an open position and a closed position, wherein, in the closed position, the first and second tissue-contacting portions cooperate to define a grasping area therebetween, the first and second jaw members adapted to connect to a source of RF energy to conduct RF energy between the tissue-contacting portions and through tissue grasped within the grasping area to treat tissue, wherein the tissue-contacting portion of each of the first jaw member and the second jaw member defines a first opening (219,229) therethrough, the first opening disposed within the grasping area and in communication with a first lumen (118,128) defined at least partially through the first jaw member, the first lumen adapted to connect to a source of vacuum to enable aspiration through the first opening, the tissue-contacting portion defining a first tissue contacting surface (214,224), a second tissue-contacting surface (218,228), and a wall (217,227) disposed between the first and second tissue-contacting surfaces, wherein the first and second tissue-contacting surfaces are offset relative to one another via a step (216,226) and the first opening is defined through the wall, characterised in that the steps of the first and the second jaw member are laterally offset relative to one another such that in an aligned orientation of the jaw members, the second tissue-contacting surface portion of the first jaw member opposes the first-tissue contacting surface portion of the second jaw member.