Abstract: A procedure and means for filtering and homogenizing liquid substances and for automatic cleaning of the filters. In the procedure are utilized an ultrasonic generator (4) connected in conjunction with the filter unit (1; 2) and ultrasonic oscillators (1.11; 2.11) thereto connected, their power and frequency being controlled on the basis of the differential pressure present across the filter units (1; 2), the liquid pressure acting in the filter unit, the liquid flow rate, signals from liquid temperature pick-ups. In order to enhance the cleaning event of the filter elements (1.2; 2.2) taking place with ultrasonics, the filter unit (1; 2) is emptied during the cleaning phase, making use of compressed air conducted into the filter. In order to facilitate the liquid filtering event and to reduce the need of cleaning action with ultrasonics, during normal filtering an ultrasonic power is maintained which is sufficient for homogenizing the liquid.