The invention relates to a combine with a cleaning device (1), having a screening device (2) with at least one screen (2A, 2B) in which the harvested products conveyed to the thresher and to the separation device are cleaned and at least one adjustable blower (3) for exposing the screening device (3) to an air flow. The width of the openings of the sifting device (2) and the revolutions of the blower (3) can be mechanically regulated by at least one regulation organ. According to the invention, at least one sensor (4) is provided whose measuring signal (S/4) directly or indirectly indicates a quantity of harvested products loaded on the combine, especially on the cleaning device. Optimal regulation of the cleaning device, especially the width of the openings of the screen, is performed by an adjusting organ (20A, 20B) depending on the signal (S/4) of the sensor (4).