A process and an apparatus determine the rheological properties of medium samples. The normal forces arising in a measuring gap perpendicular to the measuring surfaces are recorded with a recording unit and the height of the measuring gap is adjusted with a positioning unit and with positioning elements actuated by the positioning unit. During the measuring procedure the initial height of the measuring gap is kept constant, by the values of the normal forces arising being linked with a calibrating function, and in that, upon detection of normal forces arising, values derived from the calibrating function are drawn upon as control signals, with which at least one sliding actuator acting on at least one of the two measuring elements is driven, which by position adjustment or height adjustment of the respective measuring element performs an immediate resetting of a height of the measuring gap, changed by the normal forces exerted by the medium sample to be examined, to the initial spacing set originally.