Abstract: In the method of automatically controlling a continuously operating pressure filter, into which a suspension to be separated is introduced and from which a separated filtrate and a formed product, i.e. a concentrated suspension, are removed, a tolerated constant operating pressure is maintained in a filtering chamber of the pressure filter. During operation the transmission or throughput capacity of the filtering walls in the filtering chamber gradually decreases with increasing operating time of the pressure filter. To maintain, during operation, a constant ratio of the proportions of dry solid and liquid in the product the flow of suspension and the flow of product are regulated during operation in accordance with the result of measuring the transmission or throughput capacity of the filtering walls. Each time when a decrease is detected each of the two flows is reduced by the same coefficient which is directly proportional to the respectively detected decrease in the transmission capacity.