The geothermal convector (GTC) is an unconventional system for heat extraction from a geothermal aquifer without fluid withdrawal. In this system a special two-phase thermosyphon is used This device works with a downhole evaporator and with a condenser at the ground level The system shares advantages and disadvantages with other downhole heat exchanger plants; for instance a second well to return geothermal water to the aquifier is not required Because of the limitations of the natural heat flow in the hot aquifer, however; the device is most suitable for small-to moderate-size applications. In this article, the fundamental elements required to deter-mine the device performance and the thermal design criteria are reported and a GTC prototype is described. Designed for 70 degrees C temperature of the geothermal water and 3 m length of the evaporator, this prototype was recently installed in a geothermal well on the island of Ischia. In this article the results of the first experimental tests are reported.