A device and a method for controlling a two-cylinder thick matter pump comprising pistons that are actuated in a push-pull manner by means of a hydraulic reversible pump (6) and hydraulic drive cylinders controlled by said pump. To ensure a reliable operation of the pump the expected length of the stroke of the pistons (8, 8') in the drive cylinders (5, 5') is measured and recorded, the stroke time of each conveyance stroke is monitored and compared with the expected stroke duration, and the reversible pump (6) is respectively pivoted, reversing the flow, and/or the pipe switch (56) is reversed when the stroke time exceeds the expected stroke duration by a pre-determined value.