Abstract: A device for invasive temperature measurements during surface and deep hyperthermia treatments. The device includes a needle-pin element and a catheter of a biocompatible material semi-rigid sheath surrounding the needle-pin element. The needle-pin element and the sheath are coupled such that the needle-pin element can be drawn out. At least one thermocouple is provided on an outer circumference of the semi-rigid sheath of the catheter. The thermocouple has an end to affect the temperature reading and is provided close to a surface of the sheath which is in contact with tissue of a human body. Positioning means are provided at the bottom of the catheter to position the catheter adjacent to a human body and for maintaining the catheter in position.