Address. 
Department of Mathematics, School of Applied Mathematics
and Natural Science, National Technical University, Zografou Campus, Athens 15780, Greece
E-mail: mfilip@math.ntua.gr, npapg@math.ntua.gr
        
Abstract. 
We consider first order periodic
differential inclusions in  $\mathbb{R}^N$.
The presence of a subdifferential term 
incorporates in our framework differential variational  inequalities in $\mathbb{R}^N$. We establish the
existence of extremal periodic solutions and we also
obtain existence results  for the ``convex'' and ``nonconvex''problems.
AMSclassification. 34A60.
Keywords. Multifunction, convex subdifferential, extremal periodik solution, Moreanu-Yosida approximation.