The invention describes a H.F. surgical instrument for cutting and/or coagulating biological tissues, which has a metallic sleeve 12 serving as a neutral electrode and in which a metal needle 11, which serves as the cutting electrode and which is insulated against the sleeve, is arranged so as to be displaceable in the axial direction. Inside and/or outside the sleeve 12 at least one channel K; 18; 19 is provided with one connection 25; 26 each for aspiration and/or rinsing. The needle 11 which can be used as the cutting electrode can be retracted through the opening 16 intended for the purpose to such an extent that this opening in the front face 14 of the sleeve can be used as an opening for aspiration and/or rinsing.; Furthermore, there may be an additional opening 17 for aspiration and/or rinsing in the front face and/or in the vicinity of the front face of the sleeve through which aspiration and/or rinsing is possible even when the needle electrode is advanced so as to project out of its opening or when the needle electrode is retracted into the sleeve and its opening is pressed against tissue. The outer surface of the instrument is provided with an insulating layer 10 largely covering this instrument.