Abstract: In this paper by introducing a key assumption, we prove that the key assumption is equivalent to the Robinson metric regularity of the implicit multifunction and that under some suitable conditions the key assumption is sufficient for the Lipschitz-likeness (metric regularity) of the implicit multifunction. Finally, we establish the specific expressions of the contingent derivative and the second-order contingent derivative for the implicit multifunction.

Key words: implictit multifunction, Robinson metric regularity, Lipschitz-likeness, contingent derivative