Abstract: A liquid-ring pump according to the invention for use as a vacuum pump, e.g. for the aspiration of centrifugal pumps, and for use in the transport of fluids, e.g. mixtures of liquids and gases or solid particles, is of the type where the distance between the internal surface (17) of the pump housing and the rotor (10) varies. Seen in section, the surface is divided into two identical, reverse-image sectors, in relation to which the rotor (10) is disposed in a symmetrical manner. In the transition area between the two sectors the internal surface (17) is provided with a substantially flat surface (44) stretching tangentially in relation to the periphery of the rotor (10). Thereby cavitiation problems are reduced.