(57) Extrusion, especially of an aqueous ceramic composi- ! tions, is carried out under the influence of mechanical vibrations, preferably at ultrasonic frequencies in the range 15000 - 25000 Hz. This has advantages such as increasing the rate of extrusion at a given level of motive power or decreasing the extent to which compositions need to be preconsolidated before extrusion. Application of vibrations to the extrusion die facilitates cleaning after use. Extrudates can be cut cleanly by applying the vibrations to a cutting tool.