An electrosurgical instrument is provided for the treatment of tissue, the instrument comprising an instrument shaft (10) having a longitudinal axis, and an electrode assembly at one end of the shaft. The electrode assembly comprises first and second active electrodes (11), (14) and at least one return electrode (25), the electrodes being electrically insulated one from another by means of one or more insulation members (12). The first and second active electrodes (11, 14) each have an exposed surface for treating tissue, the exposed surface (19) of the first active electrode being such as to treat tissue disposed laterally of the longitudinal axis at a first radial position with respect to the instrument shaft. The exposed surface (15) of the second active electrode is such as to treat tissue disposed laterally of the longitudinal axis at a second radial position with respect to the instrument shaft. The instrument has a first set of connections by which the first active electrode (11) can be placed in circuit with the return electrode (25), and a second set of connections by which the second active electrode (14) can be placed in circuit with the return electrode (25).組織の処置のための電気外科用器具が提供され、該器具は、長手方向軸を有する器具シャフト（１０）と、該シャフトの一端にある電極アセンブリとを備える。電極アセンブリは、第１のアクティブ電極および第２のアクティブ電極（１１、１４）と、少なくとも１つのリターン電極（２５）とを備える。第１のアクティブ電極および第２のアクティブ電極（１１、１４）はそれぞれ、器具シャフトに対して第１の半径方向位置および第２の半径方向位置において長手方向軸の側方に配置された組織を処置するための露出した表面を有する。器具は、リターン電極（２５）を有する回路内に第１のアクティブ電極（１１）を配置させる第１の組の接続部と、リターン電極（２５）を有する回路内に第２のアクティブ電極（１４）を配置させる第２の組の接続部とを有する。
