For the coagulation of tissue there are known instruments, in particular probes, that are designed to deliver argon gas into a space between an electrode within the probe and the tissue. In some cases the intention is to coagulate tissues situated at the side of the outlet of the probe. The invention provides an apparatus for coagulating tissue in which the distal end of the electrode projects out of the gas-delivering device or probe, and at said distal end a guiding device for directing and guiding the gas or plasma is disposed in such a way that at least part of the flowing gas or plasma is deflected into a predetermined direction.