An apparatus for homogenizing and/or dispersing at least one viscous substance and at least one solid and/or at least one other substance of different viscosity includes in a space in a housing axis-parallel rotatable shafts disposed along a circle with equal central-angle distance and provided with tightly intermeshing screw elements. The shafts in the area outside the openings in the housing are provided with screw elements having a pitch (S) of at most three quarters of the outside screw diameter (D) over a length (L=L1+L2+L3) corresponding to at least ten times the outside diameter (D) of the screw elements.