A method and a suitable device determine the contamination of a suction roller of a machine for producing a fibrous web, in particular a paper, cardboard, tissue or pulp web. The method includes the steps of: a. flowing a fluid through a measurement area of a roller shell, wherein either the pressure or the throughflow speed of the fluid is kept constant; b. determining a characteristic variable, wherein the characteristic variable includes the resulting throughflow speed in the case of a throughflow at a constant pressure and of the resulting pressure drop in the case of the measurement at a constant throughflow speed; c. providing one or more reference variables; and d. determining a degree of contamination of the suction roller by way of comparison of the characteristic variable with the reference variable or variables.