Abstract: In a radiation coagulator having an electric incandescent lamp, in particular a tungsten-halogen low-voltage lamp, as radiation source, and a tissue contact element of a crystalline dielectric material transmissive to the radiation, forming a contact surface to be pressed against living body tissue, the temperature conductivity (reciprocal of the temperature resistance), the heat capacity of the contact element, possibly in combination with a heat sink attached thereto, is so great that the heat generated in the tissue in contact with said surface is derived in substantial measure from the tissue contact element. This prevents an over-rapid and over-intense temperature rise at the surface of the tissue, leading to a considerable improvement in coagulability, especially for severe parenchymatous hemorrhages, and to lessened adhesion to the contact surface, and permitting a gentle coagulation, extending into depth if desired.