An apparatus for continuously mixing and heating flowable materials comprises an inclined housing, at least two rotatable screws within the housing with each screw having a rotatably mounted shaft and a screw flight. The screws are arranged in parallel juxtaposition with their respective flights of opposite hand intermeshing. The shafts are driven in opposite rotation to each other and each shaft is hollow and is provided with electric heaters within the shaft for heating the flowable material.