  We analyze the conditions for getting the Casimir repulsion between two
nonequal plates. The force between plates with magnetic permeability defined by
Drude or Lorentz models is calculated. The short and long distance limits of
the force are derived. The Casimir set-up with the hypothetical perfect
matching metamaterial is discussed. We put into question the possibility of
getting repulsion within the design of metamaterials based on metallic
inclusions.
