Abstract: The invention provides an apparatus for mixing and kneading materials comprising a housing defining a mixing and kneading chamber, a jacket member enclosing the mixing and kneading chamber and a mixing and kneading member located in the interior of the mixing and kneading chamber. The mixing and kneading member is driven to a rotating and/or oscillating motion. For supporting the mixing and kneading operation, projection members are provided protruding from the jacket member into the interior of the mixing and kneading chamber. In order to simplify the design of the apparatus and, particularly, to improve the heating and cooling of the mixing and kneading chamber, at least some of the projection members are connected directly to the jacket member, or at least some of the projection members are integrally formed with the jacket member thus constituting a common jacket member/projection member unit.