The influence of shear on the demixing pressures of the binary system ethene/polyethene was determined viscometrically in the temperature range 147-195 degrees C up to pressures of 1400 bar at polymer concentrations of 18.4, 22.5 and 27.4 wt%, respectively. Autoclaves were used to prepare the solutions and to measure cloud points for the stagnant system. A high-pressure viscometer was used to perform experiments at shear rates gamma up to 1500 s(-1). Under all conditions investigated here the two-phase area grows as gamma becomes larger and the demixing pressures increase up to 23 bar. This observation is in contrast to theoretical expectation according to which it should be the one-phase region which expands under the prevailing conditions.