The frictional heat generated by higher shear rates in slitviscometers couldn't be cast off totally. The undesirable temperature rise results in a reduction of viscosity. Experiments withnewtonian fluids showed an approximate linear temperature rise in the flow direction. Fornewtonian fluids, an analytical correction method of the flow curve is demonstrated with consideration of this linear temperature distribution. With the aid of two dimensionless parameters, correction factors could be determined graphically in a simple way. These are formed with significant material constants, the temperature and pressure gradients in flow direction as well as geometrical parameters.