Abstract: A apparatus for feeding concrete and other thick materials from a container into a feeding pipe by two feeding cylinders which are alternately connectable by a switching device to the container or the feeding pipe. The feeding pistons of the feeding cylinders alternately perform a suction stroke and a pressure stroke, with the average piston speed being at least temporarily greater during the suction stroke than during the pressure stroke. A continuous feeding flow is achieved in that during the switching period t.sub.u of the switching device the two feeding cylinders are substantially separated from the container at least temporarily and are short-circuited together to form a joint conenction with the feeding pipe. In this state, the one feeding piston is still finishing its pressure stroke while the other feeding piston already begins its pressure stroke at the same time.