A distributive and dispersive mixing apparatus comprising two confronting surfaces (1,2) having cavities (3) therein which on relative motion of the surfaces function as a cavity transfer mixer (CTM) or controlled deformation dynamic mixer (CDDM) or both, CHARACTERISED IN THAT the normal separation of the confronting surfaces varies in the direction of bulk flow, so as to define a plurality of regions of successive closer and wider spacing of the confronting surfaces.