Abstract: A turbocompressor shaft seal, especially for a high-pressure turbocompressor, has each of its gas-side and atmosphere-side slide rings biased toward a rotor ring of the shaft and associated with blocking-liquid compartments which are interconnected by an annular passage aroung the rotor ring. The compartments are connected in a closed circulation path with a circulating pump and a cooler and leakage liquid is returned by a feed pump to the liquid circulation with the aid of a pressure transformer biased on one side by the gas pressure to be sealed and an adjustable spring force and, on the other side, by the pressure of the blocking liquid. The surface area ratio K between the area of the atmosphere-side slide ring biased by the blocking liquid pressure toward the rotor ring and the sealing area of the atmosphere-side slide ring is substantially 0.45 to 0.60, the thermal conductivity of the slide rings and rotor rings is greater than 250,000 N/mm.sup.